invalid data type 'str' at _convert_outputs in arrow_dataset.py
 I trying to build multi label text classifier model using Transformers lib.

I'm using Transformers NLP to load the data set, while calling trainer.train() method. It throws the following error

File "C:\***\arrow_dataset.py", line 343, in _convert_outputs
    v = command(v)
TypeError: new(): invalid data type 'str'

I'm using pyarrow 1.0.0.  And I have simple custom data set with Text and Integer Label.
Ex: Data
 Text ,     Label  #Column Header
 I'm facing an Network issue, 1
 I forgot my password, 2

Error StackTrace:

File "C:\**\transformers\trainer.py", line 492, in train
    for step, inputs in enumerate(epoch_iterator):
  File "C:\**\tqdm\std.py", line 1104, in __iter__
    for obj in iterable:
  File "C:\**\torch\utils\data\dataloader.py", line 345, in __next__
    data = self._next_data()
  File "C:\**\torch\utils\data\dataloader.py", line 385, in _next_data
    data = self._dataset_fetcher.fetch(index)  # may raise StopIteration
  File "C:\**\torch\utils\data\_utils\fetch.py", line 44, in fetch
    data = [self.dataset[idx] for idx in possibly_batched_index]
  File "C:\**\torch\utils\data\_utils\fetch.py", line 44, in <listcomp>
    data = [self.dataset[idx] for idx in possibly_batched_index]
  File "C:\**\nlp\arrow_dataset.py", line 414, in __getitem__
    output_all_columns=self._output_all_columns,
  File "C:\**\nlp\arrow_dataset.py", line 403, in _getitem
    outputs, format_type=format_type, format_columns=format_columns, output_all_columns=output_all_columns
  File "C:\**\nlp\arrow_dataset.py", line 343, in _convert_outputs
    v = command(v)
TypeError: new(): invalid data type 'str'

 Hi, actually the thing is I am getting the same error and even after tokenizing them I am passing them through batch_encode_plus.
I dont know what seems to be the problem is. I even converted it into 'pt' while passing them through batch_encode_plus but when I am evaluating my model , i am getting this error

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-145-ca218223c9fc> in <module>()
----> 1 val_loss, predictions, true_val = evaluate(dataloader_validation)
      2 val_f1 = f1_score_func(predictions, true_val)
      3 tqdm.write(f'Validation loss: {val_loss}')
      4 tqdm.write(f'F1 Score (Weighted): {val_f1}')

6 frames
/usr/local/lib/python3.6/dist-packages/torch/utils/data/dataset.py in <genexpr>(.0)
    160
    161     def __getitem__(self, index):
--> 162         return tuple(tensor[index] for tensor in self.tensors)
    163
    164     def __len__(self):

TypeError: new(): invalid data type 'str'


invalid data type 'str' at _convert_outputs in arrow_dataset.py
 I trying to build multi label text classifier model using Transformers lib.

I'm using Transformers NLP to load the data set, while calling trainer.train() method. It throws the following error

File "C:\***\arrow_dataset.py", line 343, in _convert_outputs
    v = command(v)
TypeError: new(): invalid data type 'str'

I'm using pyarrow 1.0.0.  And I have simple custom data set with Text and Integer Label.
Ex: Data
 Text ,     Label  #Column Header
 I'm facing an Network issue, 1
 I forgot my password, 2

Error StackTrace:

File "C:\**\transformers\trainer.py", line 492, in train
    for step, inputs in enumerate(epoch_iterator):
  File "C:\**\tqdm\std.py", line 1104, in __iter__
    for obj in iterable:
  File "C:\**\torch\utils\data\dataloader.py", line 345, in __next__
    data = self._next_data()
  File "C:\**\torch\utils\data\dataloader.py", line 385, in _next_data
    data = self._dataset_fetcher.fetch(index)  # may raise StopIteration
  File "C:\**\torch\utils\data\_utils\fetch.py", line 44, in fetch
    data = [self.dataset[idx] for idx in possibly_batched_index]
  File "C:\**\torch\utils\data\_utils\fetch.py", line 44, in <listcomp>
    data = [self.dataset[idx] for idx in possibly_batched_index]
  File "C:\**\nlp\arrow_dataset.py", line 414, in __getitem__
    output_all_columns=self._output_all_columns,
  File "C:\**\nlp\arrow_dataset.py", line 403, in _getitem
    outputs, format_type=format_type, format_columns=format_columns, output_all_columns=output_all_columns
  File "C:\**\nlp\arrow_dataset.py", line 343, in _convert_outputs
    v = command(v)
TypeError: new(): invalid data type 'str'

 > Hi, actually the thing is I am getting the same error and even after tokenizing them I am passing them through batch_encode_plus.
> I dont know what seems to be the problem is. I even converted it into 'pt' while passing them through batch_encode_plus but when I am evaluating my model , i am getting this error
>
> TypeError Traceback (most recent call last)
> in ()
> ----> 1 val_loss, predictions, true_val = evaluate(dataloader_validation)
> 2 val_f1 = f1_score_func(predictions, true_val)
> 3 tqdm.write(f'Validation loss: {val_loss}')
> 4 tqdm.write(f'F1 Score (Weighted): {val_f1}')
>
> 6 frames
> /usr/local/lib/python3.6/dist-packages/torch/utils/data/dataset.py in (.0)
> 160
> 161 def **getitem**(self, index):
> --> 162 return tuple(tensor[index] for tensor in self.tensors)
> 163
> 164 def **len**(self):
>
> TypeError: new(): invalid data type 'str'

I got the same error and fix it .
you can check your input where there may be string contained.
such as
```
a = [1,2,3,4,'<unk>']
torch.tensor(a)
```


invalid data type 'str' at _convert_outputs in arrow_dataset.py
 I trying to build multi label text classifier model using Transformers lib.

I'm using Transformers NLP to load the data set, while calling trainer.train() method. It throws the following error

File "C:\***\arrow_dataset.py", line 343, in _convert_outputs
    v = command(v)
TypeError: new(): invalid data type 'str'

I'm using pyarrow 1.0.0.  And I have simple custom data set with Text and Integer Label.
Ex: Data
 Text ,     Label  #Column Header
 I'm facing an Network issue, 1
 I forgot my password, 2

Error StackTrace:

File "C:\**\transformers\trainer.py", line 492, in train
    for step, inputs in enumerate(epoch_iterator):
  File "C:\**\tqdm\std.py", line 1104, in __iter__
    for obj in iterable:
  File "C:\**\torch\utils\data\dataloader.py", line 345, in __next__
    data = self._next_data()
  File "C:\**\torch\utils\data\dataloader.py", line 385, in _next_data
    data = self._dataset_fetcher.fetch(index)  # may raise StopIteration
  File "C:\**\torch\utils\data\_utils\fetch.py", line 44, in fetch
    data = [self.dataset[idx] for idx in possibly_batched_index]
  File "C:\**\torch\utils\data\_utils\fetch.py", line 44, in <listcomp>
    data = [self.dataset[idx] for idx in possibly_batched_index]
  File "C:\**\nlp\arrow_dataset.py", line 414, in __getitem__
    output_all_columns=self._output_all_columns,
  File "C:\**\nlp\arrow_dataset.py", line 403, in _getitem
    outputs, format_type=format_type, format_columns=format_columns, output_all_columns=output_all_columns
  File "C:\**\nlp\arrow_dataset.py", line 343, in _convert_outputs
    v = command(v)
TypeError: new(): invalid data type 'str'

 I didn't know tokenizers could return strings in the token ids. Which tokenizer are you using to get this @Doragd ?


invalid data type 'str' at _convert_outputs in arrow_dataset.py
 I trying to build multi label text classifier model using Transformers lib.

I'm using Transformers NLP to load the data set, while calling trainer.train() method. It throws the following error

File "C:\***\arrow_dataset.py", line 343, in _convert_outputs
    v = command(v)
TypeError: new(): invalid data type 'str'

I'm using pyarrow 1.0.0.  And I have simple custom data set with Text and Integer Label.
Ex: Data
 Text ,     Label  #Column Header
 I'm facing an Network issue, 1
 I forgot my password, 2

Error StackTrace:

File "C:\**\transformers\trainer.py", line 492, in train
    for step, inputs in enumerate(epoch_iterator):
  File "C:\**\tqdm\std.py", line 1104, in __iter__
    for obj in iterable:
  File "C:\**\torch\utils\data\dataloader.py", line 345, in __next__
    data = self._next_data()
  File "C:\**\torch\utils\data\dataloader.py", line 385, in _next_data
    data = self._dataset_fetcher.fetch(index)  # may raise StopIteration
  File "C:\**\torch\utils\data\_utils\fetch.py", line 44, in fetch
    data = [self.dataset[idx] for idx in possibly_batched_index]
  File "C:\**\torch\utils\data\_utils\fetch.py", line 44, in <listcomp>
    data = [self.dataset[idx] for idx in possibly_batched_index]
  File "C:\**\nlp\arrow_dataset.py", line 414, in __getitem__
    output_all_columns=self._output_all_columns,
  File "C:\**\nlp\arrow_dataset.py", line 403, in _getitem
    outputs, format_type=format_type, format_columns=format_columns, output_all_columns=output_all_columns
  File "C:\**\nlp\arrow_dataset.py", line 343, in _convert_outputs
    v = command(v)
TypeError: new(): invalid data type 'str'

 > I didn't know tokenizers could return strings in the token ids. Which tokenizer are you using to get this @Doragd ?

i'm sorry that i met this issue in another place (not in huggingface repo).


invalid data type 'str' at _convert_outputs in arrow_dataset.py
 I trying to build multi label text classifier model using Transformers lib.

I'm using Transformers NLP to load the data set, while calling trainer.train() method. It throws the following error

File "C:\***\arrow_dataset.py", line 343, in _convert_outputs
    v = command(v)
TypeError: new(): invalid data type 'str'

I'm using pyarrow 1.0.0.  And I have simple custom data set with Text and Integer Label.
Ex: Data
 Text ,     Label  #Column Header
 I'm facing an Network issue, 1
 I forgot my password, 2

Error StackTrace:

File "C:\**\transformers\trainer.py", line 492, in train
    for step, inputs in enumerate(epoch_iterator):
  File "C:\**\tqdm\std.py", line 1104, in __iter__
    for obj in iterable:
  File "C:\**\torch\utils\data\dataloader.py", line 345, in __next__
    data = self._next_data()
  File "C:\**\torch\utils\data\dataloader.py", line 385, in _next_data
    data = self._dataset_fetcher.fetch(index)  # may raise StopIteration
  File "C:\**\torch\utils\data\_utils\fetch.py", line 44, in fetch
    data = [self.dataset[idx] for idx in possibly_batched_index]
  File "C:\**\torch\utils\data\_utils\fetch.py", line 44, in <listcomp>
    data = [self.dataset[idx] for idx in possibly_batched_index]
  File "C:\**\nlp\arrow_dataset.py", line 414, in __getitem__
    output_all_columns=self._output_all_columns,
  File "C:\**\nlp\arrow_dataset.py", line 403, in _getitem
    outputs, format_type=format_type, format_columns=format_columns, output_all_columns=output_all_columns
  File "C:\**\nlp\arrow_dataset.py", line 343, in _convert_outputs
    v = command(v)
TypeError: new(): invalid data type 'str'

 @akhilkapil do you have strings in your dataset ? When you set the dataset format to "pytorch" you should exclude columns with strings as pytorch can't make tensors out of strings


UnicodeDecodeError while loading PAN-X task of XTREME dataset
 Hi 🤗  team!

## Description of the problem
I'm running into a `UnicodeDecodeError` while trying to load the PAN-X subset the XTREME dataset:

```
---------------------------------------------------------------------------
UnicodeDecodeError                        Traceback (most recent call last)
<ipython-input-5-1d61f439b843> in <module>
----> 1 dataset = load_dataset("xtreme", "PAN-X.en", data_dir='./data')

/usr/local/lib/python3.6/dist-packages/nlp/load.py in load_dataset(path, name, version, data_dir, data_files, split, cache_dir, features, download_config, download_mode, ignore_verifications, save_infos, **config_kwargs)
    528     ignore_verifications = ignore_verifications or save_infos
    529     # Download/copy dataset processing script
--> 530     module_path, hash = prepare_module(path, download_config=download_config, dataset=True)
    531
    532     # Get dataset builder class from the processing script

/usr/local/lib/python3.6/dist-packages/nlp/load.py in prepare_module(path, download_config, dataset, force_local_path, **download_kwargs)
    265
    266     # Download external imports if needed
--> 267     imports = get_imports(local_path)
    268     local_imports = []
    269     library_imports = []

/usr/local/lib/python3.6/dist-packages/nlp/load.py in get_imports(file_path)
    156     lines = []
    157     with open(file_path, mode="r") as f:
--> 158         lines.extend(f.readlines())
    159
    160     logger.info("Checking %s for additional imports.", file_path)

/usr/lib/python3.6/encodings/ascii.py in decode(self, input, final)
     24 class IncrementalDecoder(codecs.IncrementalDecoder):
     25     def decode(self, input, final=False):
---> 26         return codecs.ascii_decode(input, self.errors)[0]
     27
     28 class StreamWriter(Codec,codecs.StreamWriter):

UnicodeDecodeError: 'ascii' codec can't decode byte 0xe2 in position 111: ordinal not in range(128)
```

## Steps to reproduce
Install from nlp's master branch
```python
pip install git+https://github.com/huggingface/nlp.git
```
then run
```python
from nlp import load_dataset
# AmazonPhotos.zip is located in data/
dataset = load_dataset("xtreme", "PAN-X.en", data_dir='./data')
```

## OS / platform details

- `nlp` version: latest from master
- Platform: Linux-4.15.0-72-generic-x86_64-with-Ubuntu-18.04-bionic
- Python version: 3.6.9
- PyTorch version (GPU?): 1.4.0 (True)
- Tensorflow version (GPU?): 2.1.0 (True)
- Using GPU in script?: True
- Using distributed or parallel set-up in script?: False

## Proposed solution
Either change [line 762](https://github.com/huggingface/nlp/blob/7ada00b1d62f94eee22a7df38c6b01e3f27194b7/datasets/xtreme/xtreme.py#L762) in `xtreme.py` to include UTF-8 encoding:

```
# old
with open(filepath) as f
# new
with open(filepath, encoding='utf-8') as f
```

or raise a warning that suggests setting the locale explicitly, e.g.
```python
import locale
locale.setlocale(locale.LC_ALL, 'C.UTF-8')
```
I have a preference for the first solution. Let me know if you agree and I'll be happy to implement the simple fix!
 Indeed. Solution 1 is the simplest.

This is actually a recurring problem.
I think we should scan all the datasets with regexpr to fix the use of `open()` without encodings.
And probably add a test in the CI to forbid using this in the future.


UnicodeDecodeError while loading PAN-X task of XTREME dataset
 Hi 🤗  team!

## Description of the problem
I'm running into a `UnicodeDecodeError` while trying to load the PAN-X subset the XTREME dataset:

```
---------------------------------------------------------------------------
UnicodeDecodeError                        Traceback (most recent call last)
<ipython-input-5-1d61f439b843> in <module>
----> 1 dataset = load_dataset("xtreme", "PAN-X.en", data_dir='./data')

/usr/local/lib/python3.6/dist-packages/nlp/load.py in load_dataset(path, name, version, data_dir, data_files, split, cache_dir, features, download_config, download_mode, ignore_verifications, save_infos, **config_kwargs)
    528     ignore_verifications = ignore_verifications or save_infos
    529     # Download/copy dataset processing script
--> 530     module_path, hash = prepare_module(path, download_config=download_config, dataset=True)
    531
    532     # Get dataset builder class from the processing script

/usr/local/lib/python3.6/dist-packages/nlp/load.py in prepare_module(path, download_config, dataset, force_local_path, **download_kwargs)
    265
    266     # Download external imports if needed
--> 267     imports = get_imports(local_path)
    268     local_imports = []
    269     library_imports = []

/usr/local/lib/python3.6/dist-packages/nlp/load.py in get_imports(file_path)
    156     lines = []
    157     with open(file_path, mode="r") as f:
--> 158         lines.extend(f.readlines())
    159
    160     logger.info("Checking %s for additional imports.", file_path)

/usr/lib/python3.6/encodings/ascii.py in decode(self, input, final)
     24 class IncrementalDecoder(codecs.IncrementalDecoder):
     25     def decode(self, input, final=False):
---> 26         return codecs.ascii_decode(input, self.errors)[0]
     27
     28 class StreamWriter(Codec,codecs.StreamWriter):

UnicodeDecodeError: 'ascii' codec can't decode byte 0xe2 in position 111: ordinal not in range(128)
```

## Steps to reproduce
Install from nlp's master branch
```python
pip install git+https://github.com/huggingface/nlp.git
```
then run
```python
from nlp import load_dataset
# AmazonPhotos.zip is located in data/
dataset = load_dataset("xtreme", "PAN-X.en", data_dir='./data')
```

## OS / platform details

- `nlp` version: latest from master
- Platform: Linux-4.15.0-72-generic-x86_64-with-Ubuntu-18.04-bionic
- Python version: 3.6.9
- PyTorch version (GPU?): 1.4.0 (True)
- Tensorflow version (GPU?): 2.1.0 (True)
- Using GPU in script?: True
- Using distributed or parallel set-up in script?: False

## Proposed solution
Either change [line 762](https://github.com/huggingface/nlp/blob/7ada00b1d62f94eee22a7df38c6b01e3f27194b7/datasets/xtreme/xtreme.py#L762) in `xtreme.py` to include UTF-8 encoding:

```
# old
with open(filepath) as f
# new
with open(filepath, encoding='utf-8') as f
```

or raise a warning that suggests setting the locale explicitly, e.g.
```python
import locale
locale.setlocale(locale.LC_ALL, 'C.UTF-8')
```
I have a preference for the first solution. Let me know if you agree and I'll be happy to implement the simple fix!
 I've created a simple function that seems to do the trick:

```python
def apply_encoding_on_file_open(filepath: str):
    """Apply UTF-8 encoding for all instances where a non-binary file is opened."""

    with open(filepath, 'r', encoding='utf-8') as input_file:
        regexp = re.compile(r"""
                            (?!.*\b(?:encoding|rb|wb|wb+|ab|ab+)\b)
                            (open)
                            \((.*)\)
                            """)
        input_text = input_file.read()
        match = regexp.search(input_text)

        if match:
            print('Found match!', match.group())
            # append utf-8 encoding to matching groups in-place
            output = regexp.sub(lambda m: m.group()[:-1]+', encoding="utf-8")', input_text)
            with open(filepath, 'w', encoding='utf-8') as output_file:
                output_file.write(output)
        else:
            print("No match found!")
```

The regexp does a negative lookahead to avoid matching on cases where the encoding is already specified or when binary files are involved.

From an implementation perspective:

* Would it make sense to include this function in `nlp-cli` so that we can run something like
```
nlp-cli fix_encoding path/to/folder
```
and the command recursively fixes all files in the target?
* What is the desired behaviour in the CI test? Here we could either have a simple script that we run as a `job` in the CI and raises an error if a missing encoding is detected. Alternatively we could incorporate this behaviour into the CLI and run that in the CI.

Please let me know what you prefer among the alternatives.


UnicodeDecodeError while loading PAN-X task of XTREME dataset
 Hi 🤗  team!

## Description of the problem
I'm running into a `UnicodeDecodeError` while trying to load the PAN-X subset the XTREME dataset:

```
---------------------------------------------------------------------------
UnicodeDecodeError                        Traceback (most recent call last)
<ipython-input-5-1d61f439b843> in <module>
----> 1 dataset = load_dataset("xtreme", "PAN-X.en", data_dir='./data')

/usr/local/lib/python3.6/dist-packages/nlp/load.py in load_dataset(path, name, version, data_dir, data_files, split, cache_dir, features, download_config, download_mode, ignore_verifications, save_infos, **config_kwargs)
    528     ignore_verifications = ignore_verifications or save_infos
    529     # Download/copy dataset processing script
--> 530     module_path, hash = prepare_module(path, download_config=download_config, dataset=True)
    531
    532     # Get dataset builder class from the processing script

/usr/local/lib/python3.6/dist-packages/nlp/load.py in prepare_module(path, download_config, dataset, force_local_path, **download_kwargs)
    265
    266     # Download external imports if needed
--> 267     imports = get_imports(local_path)
    268     local_imports = []
    269     library_imports = []

/usr/local/lib/python3.6/dist-packages/nlp/load.py in get_imports(file_path)
    156     lines = []
    157     with open(file_path, mode="r") as f:
--> 158         lines.extend(f.readlines())
    159
    160     logger.info("Checking %s for additional imports.", file_path)

/usr/lib/python3.6/encodings/ascii.py in decode(self, input, final)
     24 class IncrementalDecoder(codecs.IncrementalDecoder):
     25     def decode(self, input, final=False):
---> 26         return codecs.ascii_decode(input, self.errors)[0]
     27
     28 class StreamWriter(Codec,codecs.StreamWriter):

UnicodeDecodeError: 'ascii' codec can't decode byte 0xe2 in position 111: ordinal not in range(128)
```

## Steps to reproduce
Install from nlp's master branch
```python
pip install git+https://github.com/huggingface/nlp.git
```
then run
```python
from nlp import load_dataset
# AmazonPhotos.zip is located in data/
dataset = load_dataset("xtreme", "PAN-X.en", data_dir='./data')
```

## OS / platform details

- `nlp` version: latest from master
- Platform: Linux-4.15.0-72-generic-x86_64-with-Ubuntu-18.04-bionic
- Python version: 3.6.9
- PyTorch version (GPU?): 1.4.0 (True)
- Tensorflow version (GPU?): 2.1.0 (True)
- Using GPU in script?: True
- Using distributed or parallel set-up in script?: False

## Proposed solution
Either change [line 762](https://github.com/huggingface/nlp/blob/7ada00b1d62f94eee22a7df38c6b01e3f27194b7/datasets/xtreme/xtreme.py#L762) in `xtreme.py` to include UTF-8 encoding:

```
# old
with open(filepath) as f
# new
with open(filepath, encoding='utf-8') as f
```

or raise a warning that suggests setting the locale explicitly, e.g.
```python
import locale
locale.setlocale(locale.LC_ALL, 'C.UTF-8')
```
I have a preference for the first solution. Let me know if you agree and I'll be happy to implement the simple fix!
 I realised I was overthinking the problem, so decided to just run the regexp over the codebase and make the PR. In other words, we can ignore my comments about using the CLI 😸


Keep loading old file even I specify a new file in load_dataset
 I used load a file called 'a.csv' by
```
dataset = load_dataset('csv', data_file='./a.csv')
```
And after a while, I tried to load another csv called 'b.csv'
```
dataset = load_dataset('csv', data_file='./b.csv')
```
However, the new dataset seems to remain the old 'a.csv' and not loading new csv file.

Even worse, after I load a.csv, the load_dataset function keeps loading the 'a.csv' afterward.

Is this a cache problem?

 This is the only fix I could come up with without touching the repo's code.
```python
from nlp.builder import FORCE_REDOWNLOAD
dataset = load_dataset('csv', data_file='./a.csv', download_mode=FORCE_REDOWNLOAD, version='0.0.1')
```
You'll have to change the version each time you want to load a different csv file.
If you're willing to add a ```print```, you can go to ```nlp.load``` and add ```print(builder_instance.cache_dir)``` right before the ```return ds``` in the ```load_dataset``` method. It'll print the cache folder, and you'll just have to erase it (and then you won't need the change here above).


Cannot unpickle saved .pt dataset with torch.save()/load()
 Saving a formatted torch dataset to file using `torch.save()`. Loading the same file fails during unpickling:

```python
>>> import torch
>>> import nlp

>>> squad = nlp.load_dataset("squad.py", split="train")
>>> squad
Dataset(features: {'source_text': Value(dtype='string', id=None), 'target_text': Value(dtype='string', id=None)}, num_rows: 87599)
>>> squad = squad.map(create_features, batched=True)
>>> squad.set_format(type="torch", columns=["source_ids", "target_ids", "attention_mask"])
>>> torch.save(squad, "squad.pt")

>>> squad_pt = torch.load("squad.pt")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/vegarab/.conda/envs/torch/lib/python3.7/site-packages/torch/serialization.py", line 593, in load
    return _legacy_load(opened_file, map_location, pickle_module, **pickle_load_args)
  File "/home/vegarab/.conda/envs/torch/lib/python3.7/site-packages/torch/serialization.py", line 773, in _legacy_load
    result = unpickler.load()
  File "/home/vegarab/.conda/envs/torch/lib/python3.7/site-packages/nlp/splits.py", line 493, in __setitem__
    raise ValueError("Cannot add elem. Use .add() instead.")
ValueError: Cannot add elem. Use .add() instead.
```
where `create_features` is a function that tokenizes the data using `batch_encode_plus` and returns a Dict with `input_ids`, `target_ids` and `attention_mask`.
```python
def create_features(batch):
    source_text_encoding = tokenizer.batch_encode_plus(
        batch["source_text"],
        max_length=max_source_length,
        pad_to_max_length=True,
        truncation=True)

    target_text_encoding = tokenizer.batch_encode_plus(
        batch["target_text"],
        max_length=max_target_length,
        pad_to_max_length=True,
        truncation=True)

    features = {
        "source_ids": source_text_encoding["input_ids"],
        "target_ids": target_text_encoding["input_ids"],
        "attention_mask": source_text_encoding["attention_mask"]
    }

    return features
```

I found a similar issue in [issue 5267 in the huggingface/transformers repo](https://github.com/huggingface/transformers/issues/5267) which was solved by downgrading to `nlp==0.2.0`. That did not solve this problem, however.
 This seems to be fixed in a non-released version.

Installing nlp from source
```
git clone https://github.com/huggingface/nlp
cd nlp
pip install .
```
solves the issue.


Issues: Adding a FAISS or Elastic Search index to a Dataset
 It seems the DPRContextEncoder, DPRContextEncoderTokenizer cited[ in this documentation](https://huggingface.co/nlp/faiss_and_ea.html) is not implemented ? It didnot work with the standard nlp installation . Also, I couldn't find or use it with the latest nlp install from github in Colab.  Is  there any dependency on the latest PyArrow 1.0.0 ? Is it yet to be made generally available ?
 `DPRContextEncoder` and `DPRContextEncoderTokenizer` will be available in the next release of `transformers`.

Right now you can experiment with it by installing `transformers` from the master branch.
You can also check the docs of DPR [here](https://huggingface.co/transformers/master/model_doc/dpr.html).

Moreover all the indexing features will also be available in the next release of `nlp`.


Issues: Adding a FAISS or Elastic Search index to a Dataset
 It seems the DPRContextEncoder, DPRContextEncoderTokenizer cited[ in this documentation](https://huggingface.co/nlp/faiss_and_ea.html) is not implemented ? It didnot work with the standard nlp installation . Also, I couldn't find or use it with the latest nlp install from github in Colab.  Is  there any dependency on the latest PyArrow 1.0.0 ? Is it yet to be made generally available ?
 @lhoestq  I tried installing transformer from the master branch. Python imports for DPR again didnt' work.  Anyways, Looking forward to trying it in the next release of nlp


New Datasets: IWSLT15+, ITTB

New Datasets: IWSLT15+, ITTB
 **Links:**
[iwslt](https://pytorchnlp.readthedocs.io/en/latest/_modules/torchnlp/datasets/iwslt.html)
Don't know if that link is up to date.

[ittb](http://www.cfilt.iitb.ac.in/iitb_parallel/)
**Motivation**: replicate mbart finetuning results (table below)
![image](https://user-images.githubusercontent.com/6045025/88490093-0c1c8c00-cf67-11ea-960d-8dcaad2aa8eb.png)

For future readers, we already have the following language pairs in the wmt namespaces:

```
wmt14: ['cs-en', 'de-en', 'fr-en', 'hi-en', 'ru-en']
wmt15: ['cs-en', 'de-en', 'fi-en', 'fr-en', 'ru-en']
wmt16: ['cs-en', 'de-en', 'fi-en', 'ro-en', 'ru-en', 'tr-en']
wmt17: ['cs-en', 'de-en', 'fi-en', 'lv-en', 'ru-en', 'tr-en', 'zh-en']
wmt18: ['cs-en', 'de-en', 'et-en', 'fi-en', 'kk-en', 'ru-en', 'tr-en', 'zh-en']
wmt19: ['cs-en', 'de-en', 'fi-en', 'gu-en', 'kk-en', 'lt-en', 'ru-en', 'zh-en', 'fr-de']
```
 Thanks Sam, we now have a very detailed tutorial and template on how to add a new dataset to the library. It typically take 1-2 hours to add one. Do you want to give it a try ?
The tutorial on writing a new dataset loading script is here: https://huggingface.co/nlp/add_dataset.html
And the part on how to share a new dataset is here: https://huggingface.co/nlp/share_dataset.html


New Datasets: IWSLT15+, ITTB

New Datasets: IWSLT15+, ITTB
 **Links:**
[iwslt](https://pytorchnlp.readthedocs.io/en/latest/_modules/torchnlp/datasets/iwslt.html)
Don't know if that link is up to date.

[ittb](http://www.cfilt.iitb.ac.in/iitb_parallel/)
**Motivation**: replicate mbart finetuning results (table below)
![image](https://user-images.githubusercontent.com/6045025/88490093-0c1c8c00-cf67-11ea-960d-8dcaad2aa8eb.png)

For future readers, we already have the following language pairs in the wmt namespaces:

```
wmt14: ['cs-en', 'de-en', 'fr-en', 'hi-en', 'ru-en']
wmt15: ['cs-en', 'de-en', 'fi-en', 'fr-en', 'ru-en']
wmt16: ['cs-en', 'de-en', 'fi-en', 'ro-en', 'ru-en', 'tr-en']
wmt17: ['cs-en', 'de-en', 'fi-en', 'lv-en', 'ru-en', 'tr-en', 'zh-en']
wmt18: ['cs-en', 'de-en', 'et-en', 'fi-en', 'kk-en', 'ru-en', 'tr-en', 'zh-en']
wmt19: ['cs-en', 'de-en', 'fi-en', 'gu-en', 'kk-en', 'lt-en', 'ru-en', 'zh-en', 'fr-de']
```
 Hi @sshleifer, I'm trying to add IWSLT using the link you provided but the download urls are not working. Only `[en, de]` pair is working. For others language pairs it throws a `404` error.


Google Colab - load_dataset - PyArrow exception
 With latest PyArrow 1.0.0 installed, I get the following exception   . Restarting colab has the same issue

ImportWarning: To use `nlp`, the module `pyarrow>=0.16.0` is required, and the current version of `pyarrow` doesn't match this condition. If you are running this in a Google Colab, you should probably just restart the runtime to use the right version of `pyarrow`.

The error goes only when I install version 0.16.0
i.e.  !pip install pyarrow==0.16.0
 +1! this is the reason our tests are failing at [TextAttack](https://github.com/QData/TextAttack)

(Though it's worth noting if we fixed the version number of pyarrow to 0.16.0 that would fix our problem too. But in this case we'll just wait for you all to update)


Google Colab - load_dataset - PyArrow exception
 With latest PyArrow 1.0.0 installed, I get the following exception   . Restarting colab has the same issue

ImportWarning: To use `nlp`, the module `pyarrow>=0.16.0` is required, and the current version of `pyarrow` doesn't match this condition. If you are running this in a Google Colab, you should probably just restart the runtime to use the right version of `pyarrow`.

The error goes only when I install version 0.16.0
i.e.  !pip install pyarrow==0.16.0
 Came to raise this issue, great to see other already have and it's being fixed so soon!

As an aside, since no one wrote this already, it seems like the version check only looks at the second part of the version number making sure it is >16, but pyarrow newest version is 1.0.0 so the second past is 0!


Google Colab - load_dataset - PyArrow exception
 With latest PyArrow 1.0.0 installed, I get the following exception   . Restarting colab has the same issue

ImportWarning: To use `nlp`, the module `pyarrow>=0.16.0` is required, and the current version of `pyarrow` doesn't match this condition. If you are running this in a Google Colab, you should probably just restart the runtime to use the right version of `pyarrow`.

The error goes only when I install version 0.16.0
i.e.  !pip install pyarrow==0.16.0
 > Indeed, we’ll make a new PyPi release next week to solve this. Cc @lhoestq

Yes definitely


ImportWarning for pyarrow 1.0.0

ImportWarning for pyarrow 1.0.0
 The following PR raised ImportWarning at `pyarrow ==1.0.0` https://github.com/huggingface/nlp/pull/265/files
 This was fixed in #434
We'll do a release later this week to include this fix.
Thanks for reporting


ImportWarning for pyarrow 1.0.0

ImportWarning for pyarrow 1.0.0
 The following PR raised ImportWarning at `pyarrow ==1.0.0` https://github.com/huggingface/nlp/pull/265/files
 I dont know if the fix was made but the problem is still present :
Instaled with pip : NLP 0.3.0 // pyarrow 1.0.0
OS : archlinux with kernel zen 5.8.5


How to reuse functionality of a (generic) dataset?
 I have written a generic dataset for corpora created with the Brat annotation tool ([specification](https://brat.nlplab.org/standoff.html), [dataset code](https://github.com/ArneBinder/nlp/blob/brat/datasets/brat/brat.py)). Now I wonder how to use that to create specific dataset instances. What's the recommended way to reuse formats and loading functionality for datasets with a common format?

In my case, it took a bit of time to create the Brat dataset and I think others would appreciate to not have to think about that again. Also, I assume there are other formats (e.g. conll) that are widely used, so having this would really ease dataset onboarding and adoption of the library.
 Hi @ArneBinder, we have a few "generic" datasets which are intended to load data files with a predefined format:
- csv: https://github.com/huggingface/nlp/tree/master/datasets/csv
- json: https://github.com/huggingface/nlp/tree/master/datasets/json
- text: https://github.com/huggingface/nlp/tree/master/datasets/text

You can find more details about this way to load datasets here in the documentation: https://huggingface.co/nlp/loading_datasets.html#from-local-files

Maybe your brat loading script could be shared in a similar fashion?


How to reuse functionality of a (generic) dataset?
 I have written a generic dataset for corpora created with the Brat annotation tool ([specification](https://brat.nlplab.org/standoff.html), [dataset code](https://github.com/ArneBinder/nlp/blob/brat/datasets/brat/brat.py)). Now I wonder how to use that to create specific dataset instances. What's the recommended way to reuse formats and loading functionality for datasets with a common format?

In my case, it took a bit of time to create the Brat dataset and I think others would appreciate to not have to think about that again. Also, I assume there are other formats (e.g. conll) that are widely used, so having this would really ease dataset onboarding and adoption of the library.
 > Maybe your brat loading script could be shared in a similar fashion?

@thomwolf that was also my first idea and I think I will tackle that in the next days. I separated the code and created a real abstract class `AbstractBrat` to allow to inherit from that (I've just seen that the dataset_loader loads the first non abstract class), now `Brat` is very similar in its functionality to https://github.com/huggingface/nlp/tree/master/datasets/text but inherits from `AbstractBrat`.

However, it is still not clear to me how to add a specific dataset (as explained in https://huggingface.co/nlp/add_dataset.html) to your repo that uses this format/abstract class, i.e. re-using the `features` entry of the  `DatasetInfo` object and `_generate_examples()`. Again, by doing so, the only remaining entries/functions to define would be `_DESCRIPTION`, `_CITATION`, `homepage` and `_URL` (which is all copy-paste stuff) and `_split_generators()`.

In a lack of better ideas, I tried sth like below, but of course it does not work outside `nlp` (`AbstractBrat` is currently defined in [datasets/brat.py](https://github.com/ArneBinder/nlp/blob/5e81fb8710546ee7be3353a7f02a3045e9a8351e/datasets/brat/brat.py)):
```python
from __future__ import absolute_import, division, print_function

import os

import nlp

from datasets.brat.brat import AbstractBrat

_CITATION = """
@inproceedings{lauscher2018b,
  title = {An argument-annotated corpus of scientific publications},
  booktitle = {Proceedings of the 5th Workshop on Mining Argumentation},
  publisher = {Association for Computational Linguistics},
  author = {Lauscher, Anne and Glava\v{s}, Goran and Ponzetto, Simone Paolo},
  address = {Brussels, Belgium},
  year = {2018},
  pages = {40–46}
}
"""

_DESCRIPTION = """\
This dataset is an extension of the Dr. Inventor corpus (Fisas et al., 2015, 2016) with an annotation layer containing
fine-grained argumentative components and relations. It is the first argument-annotated corpus of scientific
publications (in English), which allows for joint analyses of argumentation and other rhetorical dimensions of
scientific writing.
"""

_URL = "http://data.dws.informatik.uni-mannheim.de/sci-arg/compiled_corpus.zip"

class Sciarg(AbstractBrat):

    VERSION = nlp.Version("1.0.0")

    def _info(self):

        brat_features = super()._info().features
        return nlp.DatasetInfo(
            # This is the description that will appear on the datasets page.
            description=_DESCRIPTION,
            # nlp.features.FeatureConnectors
            features=brat_features,
            # If there's a common (input, target) tuple from the features,
            # specify them here. They'll be used if as_supervised=True in
            # builder.as_dataset.
            #supervised_keys=None,
            # Homepage of the dataset for documentation
            homepage="https://github.com/anlausch/ArguminSci",
            citation=_CITATION,
        )

    def _split_generators(self, dl_manager):
        """Returns SplitGenerators."""
        # TODO: Downloads the data and defines the splits
        # dl_manager is a nlp.download.DownloadManager that can be used to
        # download and extract URLs
        dl_dir = dl_manager.download_and_extract(_URL)
        data_dir = os.path.join(dl_dir, "compiled_corpus")
        print(f'data_dir: {data_dir}')
        return [
            nlp.SplitGenerator(
                name=nlp.Split.TRAIN,
                # These kwargs will be passed to _generate_examples
                gen_kwargs={
                    "directory": data_dir,
                },
            ),
        ]
```

Nevertheless, many thanks for tackling the dataset accessibility problem with this great library!


[FEATURE REQUEST] Multiprocessing with for dataset.map, dataset.filter
 It would be nice to be able to speed up `dataset.map` or `dataset.filter`. Perhaps this is as easy as sharding the dataset sending each shard to a process/thread/dask pool and using the new `nlp.concatenate_dataset()` function to join them all together?
 Yes, that would be nice. We could take a look at what tensorflow `tf.data` does under the hood for instance.


[FEATURE REQUEST] Multiprocessing with for dataset.map, dataset.filter
 It would be nice to be able to speed up `dataset.map` or `dataset.filter`. Perhaps this is as easy as sharding the dataset sending each shard to a process/thread/dask pool and using the new `nlp.concatenate_dataset()` function to join them all together?
 So `tf.data.Dataset.map()` returns a `ParallelMapDataset` if `num_parallel_calls is not None` [link](https://github.com/tensorflow/tensorflow/blob/2b96f3662bd776e277f86997659e61046b56c315/tensorflow/python/data/ops/dataset_ops.py#L1623).

There, `num_parallel_calls` is turned into a tensor and and fed to `gen_dataset_ops.parallel_map_dataset` where it looks like tensorflow takes over.

We could start with something simple like a thread or process pool that `imap`s over some shards.


[FEATURE REQUEST] Multiprocessing with for dataset.map, dataset.filter
 It would be nice to be able to speed up `dataset.map` or `dataset.filter`. Perhaps this is as easy as sharding the dataset sending each shard to a process/thread/dask pool and using the new `nlp.concatenate_dataset()` function to join them all together?
 Multiprocessing was added in #552 . You can set the number of processes with `.map(..., num_proc=...)`. It also works for `filter`

Closing this one, but feel free to reo-open if you have other questions


[FEATURE REQUEST] Multiprocessing with for dataset.map, dataset.filter
 It would be nice to be able to speed up `dataset.map` or `dataset.filter`. Perhaps this is as easy as sharding the dataset sending each shard to a process/thread/dask pool and using the new `nlp.concatenate_dataset()` function to join them all together?
 @lhoestq Great feature implemented! Do you have plans to add it to official tutorials [Processing data in a Dataset](https://huggingface.co/docs/datasets/processing.html?highlight=save#augmenting-the-dataset)? It took me sometime to find this parallel processing api.


Correct data structure for PAN-X task in XTREME dataset?
 Hi 🤗  team!

## Description of the problem
Thanks to the fix from #416 I am now able to load the NER task in the XTREME dataset as follows:

```python
from nlp import load_dataset
# AmazonPhotos.zip is located in data/
dataset = load_dataset("xtreme", "PAN-X.en", data_dir='./data')
dataset_train = dataset['train']
```

However, I am not sure that `load_dataset()` is returning the correct data structure for NER.

Currently, every row in `dataset_train` is of the form
```python
{'word': str, 'ner_tag': str, 'lang': str}
```
but I think we actually want something like
```python
{'words': List[str], 'ner_tags': List[str], 'langs': List[str]}
```
so that each row corresponds to a _sequence_ of words associated with each example. With the current data structure I do not think it is possible to transform `dataset_train` into a form suitable for training because we do not know the boundaries between examples.

Indeed, [this line](https://github.com/google-research/xtreme/blob/522434d1aece34131d997a97ce7e9242a51a688a/third_party/utils_tag.py#L58) in the XTREME repo, processes the texts as lists of sentences, tags, and languages.

## Proposed solution
Replace
```python
with open(filepath) as f:
    data = csv.reader(f, delimiter="\t", quoting=csv.QUOTE_NONE)
    for id_, row in enumerate(data):
        if row:
            lang, word = row[0].split(":")[0], row[0].split(":")[1]
            tag = row[1]
            yield id_, {"word": word, "ner_tag": tag, "lang": lang}
```
from  [these lines](https://github.com/huggingface/nlp/blob/ce7d3a1d630b78fe27188d1706f3ea980e8eec43/datasets/xtreme/xtreme.py#L881-L887) of the `_generate_examples()` function with something like

```python
guid_index = 1
with open(filepath, encoding="utf-8") as f:
    words = []
    ner_tags = []
    langs = []
    for line in f:
        if line.startswith("-DOCSTART-") or line == "" or line == "\n":
            if words:
                yield guid_index, {"words": words, "ner_tags": ner_tags, "langs": langs}
                guid_index += 1
                words = []
                ner_tags = []
        else:
            # pan-x data is tab separated
            splits = line.split("\t")
            # strip out en: prefix
            langs.append(splits[0][:2])
            words.append(splits[0][3:])
            if len(splits) > 1:
                labels.append(splits[-1].replace("\n", ""))
            else:
                # examples have no label in test set
                labels.append("O")
```
If you agree, me or @lvwerra would be happy to implement this and create a PR.
 Hi @lhoestq
I made the proposed changes to the `xtreme.py` script. I noticed that I also need to change the schema in the `dataset_infos.json` file.  More specifically the `"features"` part of the PAN-X.LANG dataset:

```json
"features":{
   "word":{
      "dtype":"string",
      "id":null,
      "_type":"Value"
   },
   "ner_tag":{
      "dtype":"string",
      "id":null,
      "_type":"Value"
   },
   "lang":{
      "dtype":"string",
      "id":null,
      "_type":"Value"
   }
}
```
To fit the code above the fields `"word"`, `"ner_tag"`, and `"lang"` would become `"words"`, `ner_tags"` and `"langs"`. In addition the `dtype` should be changed from `"string"` to `"list"`.

 I made this changes but when trying to test this locally with `dataset = load_dataset("xtreme", "PAN-X.en", data_dir='./data')` I face the issue that the `dataset_info.json` file is always overwritten by a downloaded version with the old settings, which then throws an error because the schema does not match. This makes it hard to test the changes locally. Do you have any suggestions on how to deal with that?


Correct data structure for PAN-X task in XTREME dataset?
 Hi 🤗  team!

## Description of the problem
Thanks to the fix from #416 I am now able to load the NER task in the XTREME dataset as follows:

```python
from nlp import load_dataset
# AmazonPhotos.zip is located in data/
dataset = load_dataset("xtreme", "PAN-X.en", data_dir='./data')
dataset_train = dataset['train']
```

However, I am not sure that `load_dataset()` is returning the correct data structure for NER.

Currently, every row in `dataset_train` is of the form
```python
{'word': str, 'ner_tag': str, 'lang': str}
```
but I think we actually want something like
```python
{'words': List[str], 'ner_tags': List[str], 'langs': List[str]}
```
so that each row corresponds to a _sequence_ of words associated with each example. With the current data structure I do not think it is possible to transform `dataset_train` into a form suitable for training because we do not know the boundaries between examples.

Indeed, [this line](https://github.com/google-research/xtreme/blob/522434d1aece34131d997a97ce7e9242a51a688a/third_party/utils_tag.py#L58) in the XTREME repo, processes the texts as lists of sentences, tags, and languages.

## Proposed solution
Replace
```python
with open(filepath) as f:
    data = csv.reader(f, delimiter="\t", quoting=csv.QUOTE_NONE)
    for id_, row in enumerate(data):
        if row:
            lang, word = row[0].split(":")[0], row[0].split(":")[1]
            tag = row[1]
            yield id_, {"word": word, "ner_tag": tag, "lang": lang}
```
from  [these lines](https://github.com/huggingface/nlp/blob/ce7d3a1d630b78fe27188d1706f3ea980e8eec43/datasets/xtreme/xtreme.py#L881-L887) of the `_generate_examples()` function with something like

```python
guid_index = 1
with open(filepath, encoding="utf-8") as f:
    words = []
    ner_tags = []
    langs = []
    for line in f:
        if line.startswith("-DOCSTART-") or line == "" or line == "\n":
            if words:
                yield guid_index, {"words": words, "ner_tags": ner_tags, "langs": langs}
                guid_index += 1
                words = []
                ner_tags = []
        else:
            # pan-x data is tab separated
            splits = line.split("\t")
            # strip out en: prefix
            langs.append(splits[0][:2])
            words.append(splits[0][3:])
            if len(splits) > 1:
                labels.append(splits[-1].replace("\n", ""))
            else:
                # examples have no label in test set
                labels.append("O")
```
If you agree, me or @lvwerra would be happy to implement this and create a PR.
 Hi !

You have to point to your local script.
First clone the repo and then:

```python
dataset = load_dataset("./datasets/xtreme", "PAN-X.en")
```
The "xtreme" directory contains "xtreme.py".

You also have to change the features definition in the `_info` method. You could use:

```python
features = nlp.Features({
    "words": [nlp.Value("string")],
    "ner_tags": [nlp.Value("string")],
    "langs": [nlp.Value("string")],
})
```

Hope this helps !
Let me know if you have other questions.


Correct data structure for PAN-X task in XTREME dataset?
 Hi 🤗  team!

## Description of the problem
Thanks to the fix from #416 I am now able to load the NER task in the XTREME dataset as follows:

```python
from nlp import load_dataset
# AmazonPhotos.zip is located in data/
dataset = load_dataset("xtreme", "PAN-X.en", data_dir='./data')
dataset_train = dataset['train']
```

However, I am not sure that `load_dataset()` is returning the correct data structure for NER.

Currently, every row in `dataset_train` is of the form
```python
{'word': str, 'ner_tag': str, 'lang': str}
```
but I think we actually want something like
```python
{'words': List[str], 'ner_tags': List[str], 'langs': List[str]}
```
so that each row corresponds to a _sequence_ of words associated with each example. With the current data structure I do not think it is possible to transform `dataset_train` into a form suitable for training because we do not know the boundaries between examples.

Indeed, [this line](https://github.com/google-research/xtreme/blob/522434d1aece34131d997a97ce7e9242a51a688a/third_party/utils_tag.py#L58) in the XTREME repo, processes the texts as lists of sentences, tags, and languages.

## Proposed solution
Replace
```python
with open(filepath) as f:
    data = csv.reader(f, delimiter="\t", quoting=csv.QUOTE_NONE)
    for id_, row in enumerate(data):
        if row:
            lang, word = row[0].split(":")[0], row[0].split(":")[1]
            tag = row[1]
            yield id_, {"word": word, "ner_tag": tag, "lang": lang}
```
from  [these lines](https://github.com/huggingface/nlp/blob/ce7d3a1d630b78fe27188d1706f3ea980e8eec43/datasets/xtreme/xtreme.py#L881-L887) of the `_generate_examples()` function with something like

```python
guid_index = 1
with open(filepath, encoding="utf-8") as f:
    words = []
    ner_tags = []
    langs = []
    for line in f:
        if line.startswith("-DOCSTART-") or line == "" or line == "\n":
            if words:
                yield guid_index, {"words": words, "ner_tags": ner_tags, "langs": langs}
                guid_index += 1
                words = []
                ner_tags = []
        else:
            # pan-x data is tab separated
            splits = line.split("\t")
            # strip out en: prefix
            langs.append(splits[0][:2])
            words.append(splits[0][3:])
            if len(splits) > 1:
                labels.append(splits[-1].replace("\n", ""))
            else:
                # examples have no label in test set
                labels.append("O")
```
If you agree, me or @lvwerra would be happy to implement this and create a PR.
 Thanks, I am making progress. I got a new error `NonMatchingSplitsSizesError ` (see traceback below), which I suspect is due to the fact that number of rows in the dataset changed (one row per word --> one row per sentence) as well as the number of bytes due to the slightly updated data structure.

```python
NonMatchingSplitsSizesError: [{'expected': SplitInfo(name='validation', num_bytes=1756492, num_examples=80536, dataset_name='xtreme'), 'recorded': SplitInfo(name='validation', num_bytes=1837109, num_examples=10000, dataset_name='xtreme')}, {'expected': SplitInfo(name='test', num_bytes=1752572, num_examples=80326, dataset_name='xtreme'), 'recorded': SplitInfo(name='test', num_bytes=1833214, num_examples=10000, dataset_name='xtreme')}, {'expected': SplitInfo(name='train', num_bytes=3496832, num_examples=160394, dataset_name='xtreme'), 'recorded': SplitInfo(name='train', num_bytes=3658428, num_examples=20000, dataset_name='xtreme')}]
```
I can fix the error by replacing the values in the `datasets_infos.json` file, which I tested for English. However, to update this for all 40 datasets manually is slightly painful. Is there a better way to update the expected values for all datasets?


Correct data structure for PAN-X task in XTREME dataset?
 Hi 🤗  team!

## Description of the problem
Thanks to the fix from #416 I am now able to load the NER task in the XTREME dataset as follows:

```python
from nlp import load_dataset
# AmazonPhotos.zip is located in data/
dataset = load_dataset("xtreme", "PAN-X.en", data_dir='./data')
dataset_train = dataset['train']
```

However, I am not sure that `load_dataset()` is returning the correct data structure for NER.

Currently, every row in `dataset_train` is of the form
```python
{'word': str, 'ner_tag': str, 'lang': str}
```
but I think we actually want something like
```python
{'words': List[str], 'ner_tags': List[str], 'langs': List[str]}
```
so that each row corresponds to a _sequence_ of words associated with each example. With the current data structure I do not think it is possible to transform `dataset_train` into a form suitable for training because we do not know the boundaries between examples.

Indeed, [this line](https://github.com/google-research/xtreme/blob/522434d1aece34131d997a97ce7e9242a51a688a/third_party/utils_tag.py#L58) in the XTREME repo, processes the texts as lists of sentences, tags, and languages.

## Proposed solution
Replace
```python
with open(filepath) as f:
    data = csv.reader(f, delimiter="\t", quoting=csv.QUOTE_NONE)
    for id_, row in enumerate(data):
        if row:
            lang, word = row[0].split(":")[0], row[0].split(":")[1]
            tag = row[1]
            yield id_, {"word": word, "ner_tag": tag, "lang": lang}
```
from  [these lines](https://github.com/huggingface/nlp/blob/ce7d3a1d630b78fe27188d1706f3ea980e8eec43/datasets/xtreme/xtreme.py#L881-L887) of the `_generate_examples()` function with something like

```python
guid_index = 1
with open(filepath, encoding="utf-8") as f:
    words = []
    ner_tags = []
    langs = []
    for line in f:
        if line.startswith("-DOCSTART-") or line == "" or line == "\n":
            if words:
                yield guid_index, {"words": words, "ner_tags": ner_tags, "langs": langs}
                guid_index += 1
                words = []
                ner_tags = []
        else:
            # pan-x data is tab separated
            splits = line.split("\t")
            # strip out en: prefix
            langs.append(splits[0][:2])
            words.append(splits[0][3:])
            if len(splits) > 1:
                labels.append(splits[-1].replace("\n", ""))
            else:
                # examples have no label in test set
                labels.append("O")
```
If you agree, me or @lvwerra would be happy to implement this and create a PR.
 One more thing about features. I mentioned

```python
features = nlp.Features({
    "words": [nlp.Value("string")],
    "ner_tags": [nlp.Value("string")],
    "langs": [nlp.Value("string")],
})
```

but it's actually not consistent with the way we write datasets. Something like this is simpler to read and more consistent with the way we define datasets:

```python
features = nlp.Features({
    "words": nlp.Sequence(nlp.Value("string")),
    "ner_tags": nlp.Sequence(nlp.Value("string")),
    "langs": nlp.Sequence(nlp.Value("string")),
})
```

Sorry about that


Addition of google drive links to dl_manager
 Hello there, I followed the template to create a download script of my own, which works fine for me, although I had to shun the dl_manager because it was downloading nothing from the drive links and instead use gdown.

This is the script for me:

```python
class EmoConfig(nlp.BuilderConfig):
    """BuilderConfig for SQUAD."""

    def __init__(self, **kwargs):
        """BuilderConfig for EmoContext.
    Args:
      **kwargs: keyword arguments forwarded to super.
    """
        super(EmoConfig, self).__init__(**kwargs)

_TEST_URL = "https://drive.google.com/file/d/1Hn5ytHSSoGOC4sjm3wYy0Dh0oY_oXBbb/view?usp=sharing"
_TRAIN_URL = "https://drive.google.com/file/d/12Uz59TYg_NtxOy7SXraYeXPMRT7oaO7X/view?usp=sharing"

class EmoDataset(nlp.GeneratorBasedBuilder):
    """ SemEval-2019 Task 3: EmoContext Contextual Emotion Detection in Text. Version 1.0.0 """

    VERSION = nlp.Version("1.0.0")
    force = False

    def _info(self):
        return nlp.DatasetInfo(
            description=_DESCRIPTION,
            features=nlp.Features(
                {
                    "text": nlp.Value("string"),
                    "label": nlp.features.ClassLabel(names=["others", "happy", "sad", "angry"]),
                }
            ),
            supervised_keys=None,
            homepage="https://www.aclweb.org/anthology/S19-2005/",
            citation=_CITATION,
        )

    def _get_drive_url(self, url):
        base_url = 'https://drive.google.com/uc?id='
        split_url = url.split('/')
        return base_url + split_url[5]

    def _split_generators(self, dl_manager):
        """Returns SplitGenerators."""
        if(not os.path.exists("emo-train.json") or self.force):
            gdown.download(self._get_drive_url(_TRAIN_URL), "emo-train.json", quiet = True)
        if(not os.path.exists("emo-test.json") or self.force):
            gdown.download(self._get_drive_url(_TEST_URL), "emo-test.json", quiet = True)
        return [
            nlp.SplitGenerator(
                name=nlp.Split.TRAIN,
                gen_kwargs={
                    "filepath": "emo-train.json",
                    "split": "train",
                },
            ),
            nlp.SplitGenerator(
                name=nlp.Split.TEST,
                gen_kwargs={"filepath": "emo-test.json", "split": "test"},
            ),
        ]

    def _generate_examples(self, filepath, split):
        """ Yields examples. """
        with open(filepath, 'rb') as f:
            data = json.load(f)
            for id_, text, label in zip(data["text"].keys(), data["text"].values(), data["Label"].values()):
                yield id_, {
                    "text": text,
                    "label": label,
                }
```

Can someone help me in adding gdrive links to be used with default dl_manager or adding gdown as another dl_manager, because I'd like to add this dataset to nlp's official database.
 I think the problem is the way you wrote your urls. Try the following structure to see `https://drive.google.com/uc?export=download&id=your_file_id` .

@lhoestq


Addition of google drive links to dl_manager
 Hello there, I followed the template to create a download script of my own, which works fine for me, although I had to shun the dl_manager because it was downloading nothing from the drive links and instead use gdown.

This is the script for me:

```python
class EmoConfig(nlp.BuilderConfig):
    """BuilderConfig for SQUAD."""

    def __init__(self, **kwargs):
        """BuilderConfig for EmoContext.
    Args:
      **kwargs: keyword arguments forwarded to super.
    """
        super(EmoConfig, self).__init__(**kwargs)

_TEST_URL = "https://drive.google.com/file/d/1Hn5ytHSSoGOC4sjm3wYy0Dh0oY_oXBbb/view?usp=sharing"
_TRAIN_URL = "https://drive.google.com/file/d/12Uz59TYg_NtxOy7SXraYeXPMRT7oaO7X/view?usp=sharing"

class EmoDataset(nlp.GeneratorBasedBuilder):
    """ SemEval-2019 Task 3: EmoContext Contextual Emotion Detection in Text. Version 1.0.0 """

    VERSION = nlp.Version("1.0.0")
    force = False

    def _info(self):
        return nlp.DatasetInfo(
            description=_DESCRIPTION,
            features=nlp.Features(
                {
                    "text": nlp.Value("string"),
                    "label": nlp.features.ClassLabel(names=["others", "happy", "sad", "angry"]),
                }
            ),
            supervised_keys=None,
            homepage="https://www.aclweb.org/anthology/S19-2005/",
            citation=_CITATION,
        )

    def _get_drive_url(self, url):
        base_url = 'https://drive.google.com/uc?id='
        split_url = url.split('/')
        return base_url + split_url[5]

    def _split_generators(self, dl_manager):
        """Returns SplitGenerators."""
        if(not os.path.exists("emo-train.json") or self.force):
            gdown.download(self._get_drive_url(_TRAIN_URL), "emo-train.json", quiet = True)
        if(not os.path.exists("emo-test.json") or self.force):
            gdown.download(self._get_drive_url(_TEST_URL), "emo-test.json", quiet = True)
        return [
            nlp.SplitGenerator(
                name=nlp.Split.TRAIN,
                gen_kwargs={
                    "filepath": "emo-train.json",
                    "split": "train",
                },
            ),
            nlp.SplitGenerator(
                name=nlp.Split.TEST,
                gen_kwargs={"filepath": "emo-test.json", "split": "test"},
            ),
        ]

    def _generate_examples(self, filepath, split):
        """ Yields examples. """
        with open(filepath, 'rb') as f:
            data = json.load(f)
            for id_, text, label in zip(data["text"].keys(), data["text"].values(), data["Label"].values()):
                yield id_, {
                    "text": text,
                    "label": label,
                }
```

Can someone help me in adding gdrive links to be used with default dl_manager or adding gdown as another dl_manager, because I'd like to add this dataset to nlp's official database.
 Oh sorry, I think `_get_drive_url` is doing that.

Have you tried to use `dl_manager.download_and_extract(_get_drive_url(_TRAIN_URL)`? it should work with google drive links.


from_dict delete?

from_dict delete?
 AttributeError: type object 'Dataset' has no attribute 'from_dict'
 `from_dict` was added in #350 that was unfortunately not included in the 0.3.0 release. It's going to be included in the next release that will be out pretty soon though.
Right now if you want to use `from_dict` you have to install the package from the master branch
```
pip install git+https://github.com/huggingface/nlp.git
```


from_dict delete?

from_dict delete?
 AttributeError: type object 'Dataset' has no attribute 'from_dict'
 > `from_dict` was added in #350 that was unfortunately not included in the 0.3.0 release. It's going to be included in the next release that will be out pretty soon though.
> Right now if you want to use `from_dict` you have to install the package from the master branch
>
> ```
> pip install git+https://github.com/huggingface/nlp.git
> ```
OK, thank you.


Is there a way to download only NQ dev?

Is there a way to download only NQ dev?
 Maybe I missed that in the docs, but is there a way to only download the dev set of natural questions (~1 GB)?
As we want to benchmark QA models on different datasets, I would like to avoid downloading the 41GB of training data.

I tried
```
dataset = nlp.load_dataset('natural_questions', split="validation", beam_runner="DirectRunner")
```
But this still triggered a big download of presumably the whole dataset. Is there any way of doing this or are splits / slicing options only available after downloading?

Thanks!
 Unfortunately it's not possible to download only the dev set of NQ.

I think we could add a way to download only the test set by adding a custom configuration to the processing script though.


Is there a way to download only NQ dev?

Is there a way to download only NQ dev?
 Maybe I missed that in the docs, but is there a way to only download the dev set of natural questions (~1 GB)?
As we want to benchmark QA models on different datasets, I would like to avoid downloading the 41GB of training data.

I tried
```
dataset = nlp.load_dataset('natural_questions', split="validation", beam_runner="DirectRunner")
```
But this still triggered a big download of presumably the whole dataset. Is there any way of doing this or are splits / slicing options only available after downloading?

Thanks!
 Ok, got it. I think this could be a valuable feature - especially for large datasets like NQ, but potentially also others.
For us, it will in this case make the difference of using the library or keeping the old downloads of the raw dev datasets.
However, I don't know if that fits into your plans with the library and can also understand if you don't want to support this.


Is there a way to download only NQ dev?

Is there a way to download only NQ dev?
 Maybe I missed that in the docs, but is there a way to only download the dev set of natural questions (~1 GB)?
As we want to benchmark QA models on different datasets, I would like to avoid downloading the 41GB of training data.

I tried
```
dataset = nlp.load_dataset('natural_questions', split="validation", beam_runner="DirectRunner")
```
But this still triggered a big download of presumably the whole dataset. Is there any way of doing this or are splits / slicing options only available after downloading?

Thanks!
 I don't think we could force this behavior generally since the dataset script authors are free to organize the file download as they want (sometimes the mapping between split and files can be very much nontrivial) but we can add an additional configuration for Natural Question indeed as @lhoestq indicate.


Unable to load XTREME dataset from disk

Unable to load XTREME dataset from disk
 Hi 🤗  team!

## Description of the problem
Following the [docs](https://huggingface.co/nlp/loading_datasets.html?highlight=xtreme#manually-downloading-files) I'm trying to load the `PAN-X.fr` dataset from the [XTREME](https://github.com/google-research/xtreme) benchmark.

I have manually downloaded the `AmazonPhotos.zip` file from [here](https://www.amazon.com/clouddrive/share/d3KGCRCIYwhKJF0H3eWA26hjg2ZCRhjpEQtDL70FSBN?_encoding=UTF8&%2AVersion%2A=1&%2Aentries%2A=0&mgh=1) and am running into a `FileNotFoundError` when I point to the location of the dataset.

As far as I can tell, the problem is that `AmazonPhotos.zip` decompresses to `panx_dataset` and `load_dataset()` is not looking in the correct path:

```
# path where load_dataset is looking for fr.tar.gz
/root/.cache/huggingface/datasets/9b8c4f1578e45cb2539332c79738beb3b54afbcd842b079cabfd79e3ed6704f6/
# path where it actually exists
/root/.cache/huggingface/datasets/9b8c4f1578e45cb2539332c79738beb3b54afbcd842b079cabfd79e3ed6704f6/panx_dataset/
```

## Steps to reproduce the problem

1. Manually download the XTREME benchmark from [here](https://www.amazon.com/clouddrive/share/d3KGCRCIYwhKJF0H3eWA26hjg2ZCRhjpEQtDL70FSBN?_encoding=UTF8&%2AVersion%2A=1&%2Aentries%2A=0&mgh=1)

2. Run the following code snippet
```python
from nlp import load_dataset
# AmazonPhotos.zip is in the root of the folder
dataset = load_dataset("xtreme", "PAN-X.fr", data_dir='./')
```

3. Here is the stack trace
```
---------------------------------------------------------------------------
FileNotFoundError                         Traceback (most recent call last)
<ipython-input-4-26786bb5fa93> in <module>
----> 1 dataset = load_dataset("xtreme", "PAN-X.fr", data_dir='./')

/usr/local/lib/python3.6/dist-packages/nlp/load.py in load_dataset(path, name, version, data_dir, data_files, split, cache_dir, download_config, download_mode, ignore_verifications, save_infos, **config_kwargs)
    522         download_mode=download_mode,
    523         ignore_verifications=ignore_verifications,
--> 524         save_infos=save_infos,
    525     )
    526

/usr/local/lib/python3.6/dist-packages/nlp/builder.py in download_and_prepare(self, download_config, download_mode, ignore_verifications, save_infos, try_from_hf_gcs, dl_manager, **download_and_prepare_kwargs)
    430                 verify_infos = not save_infos and not ignore_verifications
    431                 self._download_and_prepare(
--> 432                     dl_manager=dl_manager, verify_infos=verify_infos, **download_and_prepare_kwargs
    433                 )
    434                 # Sync info

/usr/local/lib/python3.6/dist-packages/nlp/builder.py in _download_and_prepare(self, dl_manager, verify_infos, **prepare_split_kwargs)
    464         split_dict = SplitDict(dataset_name=self.name)
    465         split_generators_kwargs = self._make_split_generators_kwargs(prepare_split_kwargs)
--> 466         split_generators = self._split_generators(dl_manager, **split_generators_kwargs)
    467         # Checksums verification
    468         if verify_infos:

/usr/local/lib/python3.6/dist-packages/nlp/datasets/xtreme/b8c2ed3583a7a7ac60b503576dfed3271ac86757628897e945bd329c43b8a746/xtreme.py in _split_generators(self, dl_manager)
    725             panx_dl_dir = dl_manager.extract(panx_path)
    726             lang = self.config.name.split(".")[1]
--> 727             lang_folder = dl_manager.extract(os.path.join(panx_dl_dir, lang + ".tar.gz"))
    728             return [
    729                 nlp.SplitGenerator(

/usr/local/lib/python3.6/dist-packages/nlp/utils/download_manager.py in extract(self, path_or_paths)
    196         """
    197         return map_nested(
--> 198             lambda path: cached_path(path, extract_compressed_file=True, force_extract=False), path_or_paths,
    199         )
    200

/usr/local/lib/python3.6/dist-packages/nlp/utils/py_utils.py in map_nested(function, data_struct, dict_only, map_tuple)
    170                 return tuple(mapped)
    171     # Singleton
--> 172     return function(data_struct)
    173
    174

/usr/local/lib/python3.6/dist-packages/nlp/utils/download_manager.py in <lambda>(path)
    196         """
    197         return map_nested(
--> 198             lambda path: cached_path(path, extract_compressed_file=True, force_extract=False), path_or_paths,
    199         )
    200

/usr/local/lib/python3.6/dist-packages/nlp/utils/file_utils.py in cached_path(url_or_filename, download_config, **download_kwargs)
    203     elif urlparse(url_or_filename).scheme == "":
    204         # File, but it doesn't exist.
--> 205         raise FileNotFoundError("Local file {} doesn't exist".format(url_or_filename))
    206     else:
    207         # Something unknown

FileNotFoundError: Local file /root/.cache/huggingface/datasets/9b8c4f1578e45cb2539332c79738beb3b54afbcd842b079cabfd79e3ed6704f6/fr.tar.gz doesn't exist
```

## OS and hardware
```
- `nlp` version: 0.3.0
- Platform: Linux-4.15.0-72-generic-x86_64-with-Ubuntu-18.04-bionic
- Python version: 3.6.9
- PyTorch version (GPU?): 1.4.0 (True)
- Tensorflow version (GPU?): 2.1.0 (True)
- Using GPU in script?: <fill in>
- Using distributed or parallel set-up in script?: <fill in>
```
 Hi @lewtun, you have to provide the full path to the downloaded file for example `/home/lewtum/..`


Unable to load XTREME dataset from disk

Unable to load XTREME dataset from disk
 Hi 🤗  team!

## Description of the problem
Following the [docs](https://huggingface.co/nlp/loading_datasets.html?highlight=xtreme#manually-downloading-files) I'm trying to load the `PAN-X.fr` dataset from the [XTREME](https://github.com/google-research/xtreme) benchmark.

I have manually downloaded the `AmazonPhotos.zip` file from [here](https://www.amazon.com/clouddrive/share/d3KGCRCIYwhKJF0H3eWA26hjg2ZCRhjpEQtDL70FSBN?_encoding=UTF8&%2AVersion%2A=1&%2Aentries%2A=0&mgh=1) and am running into a `FileNotFoundError` when I point to the location of the dataset.

As far as I can tell, the problem is that `AmazonPhotos.zip` decompresses to `panx_dataset` and `load_dataset()` is not looking in the correct path:

```
# path where load_dataset is looking for fr.tar.gz
/root/.cache/huggingface/datasets/9b8c4f1578e45cb2539332c79738beb3b54afbcd842b079cabfd79e3ed6704f6/
# path where it actually exists
/root/.cache/huggingface/datasets/9b8c4f1578e45cb2539332c79738beb3b54afbcd842b079cabfd79e3ed6704f6/panx_dataset/
```

## Steps to reproduce the problem

1. Manually download the XTREME benchmark from [here](https://www.amazon.com/clouddrive/share/d3KGCRCIYwhKJF0H3eWA26hjg2ZCRhjpEQtDL70FSBN?_encoding=UTF8&%2AVersion%2A=1&%2Aentries%2A=0&mgh=1)

2. Run the following code snippet
```python
from nlp import load_dataset
# AmazonPhotos.zip is in the root of the folder
dataset = load_dataset("xtreme", "PAN-X.fr", data_dir='./')
```

3. Here is the stack trace
```
---------------------------------------------------------------------------
FileNotFoundError                         Traceback (most recent call last)
<ipython-input-4-26786bb5fa93> in <module>
----> 1 dataset = load_dataset("xtreme", "PAN-X.fr", data_dir='./')

/usr/local/lib/python3.6/dist-packages/nlp/load.py in load_dataset(path, name, version, data_dir, data_files, split, cache_dir, download_config, download_mode, ignore_verifications, save_infos, **config_kwargs)
    522         download_mode=download_mode,
    523         ignore_verifications=ignore_verifications,
--> 524         save_infos=save_infos,
    525     )
    526

/usr/local/lib/python3.6/dist-packages/nlp/builder.py in download_and_prepare(self, download_config, download_mode, ignore_verifications, save_infos, try_from_hf_gcs, dl_manager, **download_and_prepare_kwargs)
    430                 verify_infos = not save_infos and not ignore_verifications
    431                 self._download_and_prepare(
--> 432                     dl_manager=dl_manager, verify_infos=verify_infos, **download_and_prepare_kwargs
    433                 )
    434                 # Sync info

/usr/local/lib/python3.6/dist-packages/nlp/builder.py in _download_and_prepare(self, dl_manager, verify_infos, **prepare_split_kwargs)
    464         split_dict = SplitDict(dataset_name=self.name)
    465         split_generators_kwargs = self._make_split_generators_kwargs(prepare_split_kwargs)
--> 466         split_generators = self._split_generators(dl_manager, **split_generators_kwargs)
    467         # Checksums verification
    468         if verify_infos:

/usr/local/lib/python3.6/dist-packages/nlp/datasets/xtreme/b8c2ed3583a7a7ac60b503576dfed3271ac86757628897e945bd329c43b8a746/xtreme.py in _split_generators(self, dl_manager)
    725             panx_dl_dir = dl_manager.extract(panx_path)
    726             lang = self.config.name.split(".")[1]
--> 727             lang_folder = dl_manager.extract(os.path.join(panx_dl_dir, lang + ".tar.gz"))
    728             return [
    729                 nlp.SplitGenerator(

/usr/local/lib/python3.6/dist-packages/nlp/utils/download_manager.py in extract(self, path_or_paths)
    196         """
    197         return map_nested(
--> 198             lambda path: cached_path(path, extract_compressed_file=True, force_extract=False), path_or_paths,
    199         )
    200

/usr/local/lib/python3.6/dist-packages/nlp/utils/py_utils.py in map_nested(function, data_struct, dict_only, map_tuple)
    170                 return tuple(mapped)
    171     # Singleton
--> 172     return function(data_struct)
    173
    174

/usr/local/lib/python3.6/dist-packages/nlp/utils/download_manager.py in <lambda>(path)
    196         """
    197         return map_nested(
--> 198             lambda path: cached_path(path, extract_compressed_file=True, force_extract=False), path_or_paths,
    199         )
    200

/usr/local/lib/python3.6/dist-packages/nlp/utils/file_utils.py in cached_path(url_or_filename, download_config, **download_kwargs)
    203     elif urlparse(url_or_filename).scheme == "":
    204         # File, but it doesn't exist.
--> 205         raise FileNotFoundError("Local file {} doesn't exist".format(url_or_filename))
    206     else:
    207         # Something unknown

FileNotFoundError: Local file /root/.cache/huggingface/datasets/9b8c4f1578e45cb2539332c79738beb3b54afbcd842b079cabfd79e3ed6704f6/fr.tar.gz doesn't exist
```

## OS and hardware
```
- `nlp` version: 0.3.0
- Platform: Linux-4.15.0-72-generic-x86_64-with-Ubuntu-18.04-bionic
- Python version: 3.6.9
- PyTorch version (GPU?): 1.4.0 (True)
- Tensorflow version (GPU?): 2.1.0 (True)
- Using GPU in script?: <fill in>
- Using distributed or parallel set-up in script?: <fill in>
```
 I was able to repro. Opening a PR to fix that.
Thanks for reporting this issue !


MissingBeamOptions for Wikipedia 20200501.en
 There may or may not be a regression for the pre-processed Wikipedia dataset. This was working fine 10 commits ago (without having Apache Beam available):

```
nlp.load_dataset('wikipedia', "20200501.en", split='train')
```

And now, having pulled master, I get:

```
Downloading and preparing dataset wikipedia/20200501.en (download: 16.99 GiB, generated: 17.07 GiB, total: 34.06 GiB) to /home/hltcoe/mgordon/.cache/huggingface/datasets/wikipedia/20200501.en/1.0.0/76b0b2747b679bb0ee7a1621e50e5a6378477add0c662668a324a5bc07d516dd...
Traceback (most recent call last):
  File "scripts/download.py", line 11, in <module>
    fire.Fire(download_pretrain)
  File "/home/hltcoe/mgordon/.conda/envs/huggingface/lib/python3.6/site-packages/fire/core.py", line 138, in Fire
    component_trace = _Fire(component, args, parsed_flag_args, context, name)
  File "/home/hltcoe/mgordon/.conda/envs/huggingface/lib/python3.6/site-packages/fire/core.py", line 468, in _Fire
    target=component.__name__)
  File "/home/hltcoe/mgordon/.conda/envs/huggingface/lib/python3.6/site-packages/fire/core.py", line 672, in _CallAndUpdateTrace
    component = fn(*varargs, **kwargs)
  File "scripts/download.py", line 6, in download_pretrain
    nlp.load_dataset('wikipedia', "20200501.en", split='train')
  File "/exp/mgordon/nlp/src/nlp/load.py", line 534, in load_dataset
    save_infos=save_infos,
  File "/exp/mgordon/nlp/src/nlp/builder.py", line 460, in download_and_prepare
    dl_manager=dl_manager, verify_infos=verify_infos, **download_and_prepare_kwargs
  File "/exp/mgordon/nlp/src/nlp/builder.py", line 870, in _download_and_prepare
    "\n\t`{}`".format(usage_example)
nlp.builder.MissingBeamOptions: Trying to generate a dataset using Apache Beam, yet no Beam Runner or PipelineOptions() has been provided in `load_dataset` or in the builder arguments. For big datasets it has to run on large-scale data processing tools like Dataflow, S
park, etc. More information about Apache Beam runners at https://beam.apache.org/documentation/runners/capability-matrix/
If you really want to run it locally because you feel like the Dataset is small enough, you can use the local beam runner called `DirectRunner` (you may run out of memory).
Example of usage:
        `load_dataset('wikipedia', '20200501.en', beam_runner='DirectRunner')`
```
 Fixed. Could you try again @mitchellgordon95 ?
It was due a file not being updated on S3.

We need to make sure all the datasets scripts get updated properly @julien-c


MissingBeamOptions for Wikipedia 20200501.en
 There may or may not be a regression for the pre-processed Wikipedia dataset. This was working fine 10 commits ago (without having Apache Beam available):

```
nlp.load_dataset('wikipedia', "20200501.en", split='train')
```

And now, having pulled master, I get:

```
Downloading and preparing dataset wikipedia/20200501.en (download: 16.99 GiB, generated: 17.07 GiB, total: 34.06 GiB) to /home/hltcoe/mgordon/.cache/huggingface/datasets/wikipedia/20200501.en/1.0.0/76b0b2747b679bb0ee7a1621e50e5a6378477add0c662668a324a5bc07d516dd...
Traceback (most recent call last):
  File "scripts/download.py", line 11, in <module>
    fire.Fire(download_pretrain)
  File "/home/hltcoe/mgordon/.conda/envs/huggingface/lib/python3.6/site-packages/fire/core.py", line 138, in Fire
    component_trace = _Fire(component, args, parsed_flag_args, context, name)
  File "/home/hltcoe/mgordon/.conda/envs/huggingface/lib/python3.6/site-packages/fire/core.py", line 468, in _Fire
    target=component.__name__)
  File "/home/hltcoe/mgordon/.conda/envs/huggingface/lib/python3.6/site-packages/fire/core.py", line 672, in _CallAndUpdateTrace
    component = fn(*varargs, **kwargs)
  File "scripts/download.py", line 6, in download_pretrain
    nlp.load_dataset('wikipedia', "20200501.en", split='train')
  File "/exp/mgordon/nlp/src/nlp/load.py", line 534, in load_dataset
    save_infos=save_infos,
  File "/exp/mgordon/nlp/src/nlp/builder.py", line 460, in download_and_prepare
    dl_manager=dl_manager, verify_infos=verify_infos, **download_and_prepare_kwargs
  File "/exp/mgordon/nlp/src/nlp/builder.py", line 870, in _download_and_prepare
    "\n\t`{}`".format(usage_example)
nlp.builder.MissingBeamOptions: Trying to generate a dataset using Apache Beam, yet no Beam Runner or PipelineOptions() has been provided in `load_dataset` or in the builder arguments. For big datasets it has to run on large-scale data processing tools like Dataflow, S
park, etc. More information about Apache Beam runners at https://beam.apache.org/documentation/runners/capability-matrix/
If you really want to run it locally because you feel like the Dataset is small enough, you can use the local beam runner called `DirectRunner` (you may run out of memory).
Example of usage:
        `load_dataset('wikipedia', '20200501.en', beam_runner='DirectRunner')`
```
 I found the same issue with almost any language other than English. (For English, it works). Will someone need to update the file on S3 again?


MissingBeamOptions for Wikipedia 20200501.en
 There may or may not be a regression for the pre-processed Wikipedia dataset. This was working fine 10 commits ago (without having Apache Beam available):

```
nlp.load_dataset('wikipedia', "20200501.en", split='train')
```

And now, having pulled master, I get:

```
Downloading and preparing dataset wikipedia/20200501.en (download: 16.99 GiB, generated: 17.07 GiB, total: 34.06 GiB) to /home/hltcoe/mgordon/.cache/huggingface/datasets/wikipedia/20200501.en/1.0.0/76b0b2747b679bb0ee7a1621e50e5a6378477add0c662668a324a5bc07d516dd...
Traceback (most recent call last):
  File "scripts/download.py", line 11, in <module>
    fire.Fire(download_pretrain)
  File "/home/hltcoe/mgordon/.conda/envs/huggingface/lib/python3.6/site-packages/fire/core.py", line 138, in Fire
    component_trace = _Fire(component, args, parsed_flag_args, context, name)
  File "/home/hltcoe/mgordon/.conda/envs/huggingface/lib/python3.6/site-packages/fire/core.py", line 468, in _Fire
    target=component.__name__)
  File "/home/hltcoe/mgordon/.conda/envs/huggingface/lib/python3.6/site-packages/fire/core.py", line 672, in _CallAndUpdateTrace
    component = fn(*varargs, **kwargs)
  File "scripts/download.py", line 6, in download_pretrain
    nlp.load_dataset('wikipedia', "20200501.en", split='train')
  File "/exp/mgordon/nlp/src/nlp/load.py", line 534, in load_dataset
    save_infos=save_infos,
  File "/exp/mgordon/nlp/src/nlp/builder.py", line 460, in download_and_prepare
    dl_manager=dl_manager, verify_infos=verify_infos, **download_and_prepare_kwargs
  File "/exp/mgordon/nlp/src/nlp/builder.py", line 870, in _download_and_prepare
    "\n\t`{}`".format(usage_example)
nlp.builder.MissingBeamOptions: Trying to generate a dataset using Apache Beam, yet no Beam Runner or PipelineOptions() has been provided in `load_dataset` or in the builder arguments. For big datasets it has to run on large-scale data processing tools like Dataflow, S
park, etc. More information about Apache Beam runners at https://beam.apache.org/documentation/runners/capability-matrix/
If you really want to run it locally because you feel like the Dataset is small enough, you can use the local beam runner called `DirectRunner` (you may run out of memory).
Example of usage:
        `load_dataset('wikipedia', '20200501.en', beam_runner='DirectRunner')`
```
 This is because only some languages are already preprocessed (en, de, fr, it) and stored on our google storage.
We plan to have a systematic way to preprocess more wikipedia languages in the future.

For the other languages you have to process them on your side using apache beam. That's why the lib asks for a Beam runner.


Faster Shuffling?

Faster Shuffling?
 Consider shuffling bookcorpus:

```
dataset = nlp.load_dataset('bookcorpus', split='train')
dataset.shuffle()
```
According to tqdm, this will take around 2.5 hours on my machine to complete (even with the faster version of select from #405). I've also tried with `keep_in_memory=True` and `writer_batch_size=1000`.

But I can also just write the lines to a text file:

```
batch_size = 100000
with open('tmp.txt', 'w+') as out_f:
    for i in tqdm(range(0, len(dataset), batch_size)):
        batch = dataset[i:i+batch_size]['text']
        print("\n".join(batch), file=out_f)
```

Which completes in a couple minutes, followed by `shuf tmp.txt > tmp2.txt` which completes in under a minute. And finally,

```
dataset = nlp.load_dataset('text', data_files='tmp2.txt')
```

Which completes in under 10 minutes. I read up on Apache Arrow this morning, and it seems like the columnar data format is not especially well-suited to shuffling rows, since moving items around requires a lot of book-keeping.

Is shuffle inherently slow, or am I just using it wrong? And if it is slow, would it make sense to try converting the data to a row-based format on disk and then shuffling? (Instead of calling select with a random permutation, as is currently done.)
 I think the slowness here probably come from the fact that we are copying from and to python.

@lhoestq for all the `select`-based methods I think we should stay in Arrow format and update the writer so that it can accept Arrow tables or batches as well. What do you think?


Faster Shuffling?

Faster Shuffling?
 Consider shuffling bookcorpus:

```
dataset = nlp.load_dataset('bookcorpus', split='train')
dataset.shuffle()
```
According to tqdm, this will take around 2.5 hours on my machine to complete (even with the faster version of select from #405). I've also tried with `keep_in_memory=True` and `writer_batch_size=1000`.

But I can also just write the lines to a text file:

```
batch_size = 100000
with open('tmp.txt', 'w+') as out_f:
    for i in tqdm(range(0, len(dataset), batch_size)):
        batch = dataset[i:i+batch_size]['text']
        print("\n".join(batch), file=out_f)
```

Which completes in a couple minutes, followed by `shuf tmp.txt > tmp2.txt` which completes in under a minute. And finally,

```
dataset = nlp.load_dataset('text', data_files='tmp2.txt')
```

Which completes in under 10 minutes. I read up on Apache Arrow this morning, and it seems like the columnar data format is not especially well-suited to shuffling rows, since moving items around requires a lot of book-keeping.

Is shuffle inherently slow, or am I just using it wrong? And if it is slow, would it make sense to try converting the data to a row-based format on disk and then shuffling? (Instead of calling select with a random permutation, as is currently done.)
 > @lhoestq for all the `select`-based methods I think we should stay in Arrow format and update the writer so that it can accept Arrow tables or batches as well. What do you think?

I just tried with `writer.write_table` with tables of 1000 elements and it's slower that the solution in #405

On my side (select 10 000 examples):
- Original implementation: 12s
- Batched solution: 100ms
- solution using arrow tables: 350ms

I'll try with arrays and record batches to see if we can make it work.


Faster Shuffling?

Faster Shuffling?
 Consider shuffling bookcorpus:

```
dataset = nlp.load_dataset('bookcorpus', split='train')
dataset.shuffle()
```
According to tqdm, this will take around 2.5 hours on my machine to complete (even with the faster version of select from #405). I've also tried with `keep_in_memory=True` and `writer_batch_size=1000`.

But I can also just write the lines to a text file:

```
batch_size = 100000
with open('tmp.txt', 'w+') as out_f:
    for i in tqdm(range(0, len(dataset), batch_size)):
        batch = dataset[i:i+batch_size]['text']
        print("\n".join(batch), file=out_f)
```

Which completes in a couple minutes, followed by `shuf tmp.txt > tmp2.txt` which completes in under a minute. And finally,

```
dataset = nlp.load_dataset('text', data_files='tmp2.txt')
```

Which completes in under 10 minutes. I read up on Apache Arrow this morning, and it seems like the columnar data format is not especially well-suited to shuffling rows, since moving items around requires a lot of book-keeping.

Is shuffle inherently slow, or am I just using it wrong? And if it is slow, would it make sense to try converting the data to a row-based format on disk and then shuffling? (Instead of calling select with a random permutation, as is currently done.)
 I tried using `.take` from pyarrow recordbatches but it doesn't improve the speed that much:
```python
import nlp
import numpy as np

dset = nlp.Dataset.from_file("dummy_test_select.arrow")  # dummy dataset with 100000 examples like {"a": "h"*512}
indices = np.random.randint(0, 100_000, 1000_000)
```

```python
%%time
batch_size = 10_000
writer = ArrowWriter(schema=dset.schema, path="dummy_path",
                     writer_batch_size=1000, disable_nullable=False)
for i in tqdm(range(0, len(indices), batch_size)):
    table = pa.concat_tables(dset._data.slice(int(i), 1) for i in indices[i : min(len(indices), i + batch_size)])
    batch = table.to_pydict()
    writer.write_batch(batch)
writer.finalize()
# 9.12s
```

```python
%%time
batch_size = 10_000
writer = ArrowWriter(schema=dset.schema, path="dummy_path",
                     writer_batch_size=1000, disable_nullable=False)
for i in tqdm(range(0, len(indices), batch_size)):
    batch_indices = indices[i : min(len(indices), i + batch_size)]
    # First, extract only the indices that we need with a mask
    mask = [False] * len(dset)
    for k in batch_indices:
        mask[k] = True
    t_batch = dset._data.filter(pa.array(mask))
    # Second, build the list of indices for the filtered table, and taking care of duplicates
    rev_positions = {}
    duplicates = 0
    for i, j in enumerate(sorted(batch_indices)):
        if j in rev_positions:
            duplicates += 1
        else:
            rev_positions[j] = i - duplicates
    rev_map = [rev_positions[j] for j in batch_indices]
    # Third, use `.take` from the combined recordbatch
    t_combined = t_batch.combine_chunks()  # load in memory
    recordbatch = t_combined.to_batches()[0]
    table = pa.Table.from_arrays(
        [recordbatch[c].take(pa.array(rev_map)) for c in range(len(dset._data.column_names))],
        schema=writer.schema
    )
    writer.write_table(table)
writer.finalize()
# 3.2s
```


Faster Shuffling?

Faster Shuffling?
 Consider shuffling bookcorpus:

```
dataset = nlp.load_dataset('bookcorpus', split='train')
dataset.shuffle()
```
According to tqdm, this will take around 2.5 hours on my machine to complete (even with the faster version of select from #405). I've also tried with `keep_in_memory=True` and `writer_batch_size=1000`.

But I can also just write the lines to a text file:

```
batch_size = 100000
with open('tmp.txt', 'w+') as out_f:
    for i in tqdm(range(0, len(dataset), batch_size)):
        batch = dataset[i:i+batch_size]['text']
        print("\n".join(batch), file=out_f)
```

Which completes in a couple minutes, followed by `shuf tmp.txt > tmp2.txt` which completes in under a minute. And finally,

```
dataset = nlp.load_dataset('text', data_files='tmp2.txt')
```

Which completes in under 10 minutes. I read up on Apache Arrow this morning, and it seems like the columnar data format is not especially well-suited to shuffling rows, since moving items around requires a lot of book-keeping.

Is shuffle inherently slow, or am I just using it wrong? And if it is slow, would it make sense to try converting the data to a row-based format on disk and then shuffling? (Instead of calling select with a random permutation, as is currently done.)
 Shuffling is now significantly faster thanks to #513
Feel free to play with it now :)

Closing this one, but feel free to re-open if you have other questions


🐛 [Dataset] Cannot download wmt14, wmt15 and wmt17
 1. I try downloading `wmt14`, `wmt15`, `wmt17`, `wmt19` with the following code:
```
nlp.load_dataset('wmt14','de-en')
nlp.load_dataset('wmt15','de-en')
nlp.load_dataset('wmt17','de-en')
nlp.load_dataset('wmt19','de-en')
```
The code runs but the download speed is **extremely slow**, the same behaviour is not observed on `wmt16` and `wmt18`

2. When trying to download `wmt17 zh-en`, I got the following error:
> ConnectionError: Couldn't reach https://storage.googleapis.com/tfdataset-data/downloadataset/uncorpus/UNv1.0.en-zh.tar.gz
 similar slow download speed here for nlp.load_dataset('wmt14', 'fr-en')
`
Downloading: 100%|██████████████████████████████████████████████████████████| 658M/658M [1:00:42<00:00, 181kB/s]
Downloading: 100%|██████████████████████████████████████████████████████████| 918M/918M [1:39:38<00:00, 154kB/s]
Downloading:   2%|▉                                                       | 40.9M/2.37G [04:48<5:03:06, 128kB/s]
`
Could we just download a specific subdataset in 'wmt14', such as 'newstest14'?


🐛 [Dataset] Cannot download wmt14, wmt15 and wmt17
 1. I try downloading `wmt14`, `wmt15`, `wmt17`, `wmt19` with the following code:
```
nlp.load_dataset('wmt14','de-en')
nlp.load_dataset('wmt15','de-en')
nlp.load_dataset('wmt17','de-en')
nlp.load_dataset('wmt19','de-en')
```
The code runs but the download speed is **extremely slow**, the same behaviour is not observed on `wmt16` and `wmt18`

2. When trying to download `wmt17 zh-en`, I got the following error:
> ConnectionError: Couldn't reach https://storage.googleapis.com/tfdataset-data/downloadataset/uncorpus/UNv1.0.en-zh.tar.gz
 > The code runs but the download speed is extremely slow, the same behaviour is not observed on wmt16 and wmt18

The original source for the files may provide slow download speeds.
We can probably host these files ourselves.

> When trying to download wmt17 zh-en, I got the following error:
> ConnectionError: Couldn't reach https://storage.googleapis.com/tfdataset-data/downloadataset/uncorpus/UNv1.0.en-zh.tar.gz

Looks like the file`UNv1.0.en-zh.tar.gz` is missing, or the url changed. We need to fix that

> Could we just download a specific subdataset in 'wmt14', such as 'newstest14'?

Right now I don't think it's possible. Maybe @patrickvonplaten knows more about it


🐛 [Dataset] Cannot download wmt14, wmt15 and wmt17
 1. I try downloading `wmt14`, `wmt15`, `wmt17`, `wmt19` with the following code:
```
nlp.load_dataset('wmt14','de-en')
nlp.load_dataset('wmt15','de-en')
nlp.load_dataset('wmt17','de-en')
nlp.load_dataset('wmt19','de-en')
```
The code runs but the download speed is **extremely slow**, the same behaviour is not observed on `wmt16` and `wmt18`

2. When trying to download `wmt17 zh-en`, I got the following error:
> ConnectionError: Couldn't reach https://storage.googleapis.com/tfdataset-data/downloadataset/uncorpus/UNv1.0.en-zh.tar.gz
 Yeah, the download speed is sadly always extremely slow :-/.
I will try to check out the `wmt17 zh-en` bug :-)


Conversion through to_pandas output numpy arrays for lists instead of python objects
 In a related question, the conversion through to_pandas output numpy arrays for the lists instead of python objects.

Here is an example:
```python
>>> dataset._data.slice(key, 1).to_pandas().to_dict("list")
{'sentence1': ['Amrozi accused his brother , whom he called " the witness " , of deliberately distorting his evidence .'], 'sentence2': ['Referring to him as only " the witness " , Amrozi accused his brother of deliberately distorting his evidence .'], 'label': [1], 'idx': [0], 'input_ids': [array([  101,  7277,  2180,  5303,  4806,  1117,  1711,   117,  2292,
        1119,  1270,   107,  1103,  7737,   107,   117,  1104,  9938,
        4267, 12223, 21811,  1117,  2554,   119,   102])], 'token_type_ids': [array([0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
       0, 0, 0])], 'attention_mask': [array([1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
       1, 1, 1])]}
>>> type(dataset._data.slice(key, 1).to_pandas().to_dict("list")['input_ids'][0])
<class 'numpy.ndarray'>
>>> dataset._data.slice(key, 1).to_pydict()
{'sentence1': ['Amrozi accused his brother , whom he called " the witness " , of deliberately distorting his evidence .'], 'sentence2': ['Referring to him as only " the witness " , Amrozi accused his brother of deliberately distorting his evidence .'], 'label': [1], 'idx': [0], 'input_ids': [[101, 7277, 2180, 5303, 4806, 1117, 1711, 117, 2292, 1119, 1270, 107, 1103, 7737, 107, 117, 1104, 9938, 4267, 12223, 21811, 1117, 2554, 119, 102]], 'token_type_ids': [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]], 'attention_mask': [[1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1]]}
```
 To convert from arrow type we have three options: to_numpy, to_pandas and to_pydict/to_pylist.

- to_numpy and to_pandas return numpy arrays instead of lists but are very fast.
- to_pydict/to_pylist can be 100x slower and become the bottleneck for reading data, but at least they return lists.

Maybe we can have to_pydict/to_pylist as the default and use to_numpy or to_pandas when the format (set by `set_format`) is 'numpy' or 'pandas'


[dataset] Structure of MLQA seems unecessary nested
 The features of the MLQA dataset comprise several nested dictionaries with a single element inside (for `questions` and `ids`): https://github.com/huggingface/nlp/blob/master/datasets/mlqa/mlqa.py#L90-L97

Should we keep this @mariamabarham @patrickvonplaten? Was this added for compatibility with tfds?

```python
            features=nlp.Features(
                {
                    "context": nlp.Value("string"),
                    "questions": nlp.features.Sequence({"question": nlp.Value("string")}),
                    "answers": nlp.features.Sequence(
                        {"text": nlp.Value("string"), "answer_start": nlp.Value("int32"),}
                    ),
                    "ids": nlp.features.Sequence({"idx": nlp.Value("string")})
```
 Same for the RACE dataset: https://github.com/huggingface/nlp/blob/master/datasets/race/race.py

Should we scan all the datasets to remove this pattern of un-necessary nesting?