CLN: Refactor string special methods
closes #4090, #3231
- The internal `pandas` class hierarchy has changed (slightly). The
  previous `PandasObject` now is called `PandasContainer` and a new
  `PandasObject` has become the baseclass for `PandasContainer` as well
  as `Index`, `Categorical`, `GroupBy`, `SparseList`, and
  `SparseArray` (+ their base classes). Currently, `PandasObject`
  provides string methods (from `StringMixin`).
- New `StringMixin` that, given a `__unicode__` method, gets python 2 and
  python 3 compatible string methods (`__str__`, `__bytes__`, and
  `__repr__`). Now employed in many places throughout the pandas library.
- Tried to improve safe unicode handling (e.g., where user/external input is
  used in the string or repr methods of a library).

I'm hoping to use this for the new objects in the MultiIndex naming PR, so
hopefully it's okay to merge for v0.12.

Can squash this into fewer commits if you want ... just like to lay out the changes clearly for people to review.
 are there any major api changes here?
 ahem _user facing_ api changes is what i meant :)
 This doesn't change any user-facing API at all. It does change the default NDFrame `__unicode__`/`__repr__` (which is overridden on all the standard pandas objects anyways), but aside from that doesn't change anything.
 this would close #3231 the only remaining questions is do we need a PandasScalar ?
 I didn't put this into Period or TimeStamp - should it go there too?
(wasn't sure if it would be overkill...)

On Sun, Jun 30, 2013 at 11:15 PM, jreback notifications@github.com wrote:

> this would close #3231 https://github.com/pydata/pandas/issues/3231 the
> only remaining questions is do we need a PandasScalar ?
> 
> —
> Reply to this email directly or view it on GitHubhttps://github.com/pydata/pandas/pull/4092#issuecomment-20261588
> .
 would it make string methods in Period-Timestamp ?
 what purpose would `PandasScalar` serve? unifying the repring API of the various scalar types? might be useful if there are more scalar types planned, e.g., `Timedelta`
 Side note: added PandasObject to `Block` and `BlockManager` in internals and to `Period` too.
 my question is are there ops on scalars that are useful outside of their role in arrays and repring themselves, personally i almost never use the scalar versions for anything except inspection
 also is there a problem with moving `_constructor` into `PandasObject`?
 No. Would that just be `return self.__class__` unless overridden?

On Sun, Jun 30, 2013 at 11:46 PM, Phillip Cloud notifications@github.comwrote:

> also is there a problem with moving _constructor into PandasObject?
> 
> —
> Reply to this email directly or view it on GitHubhttps://github.com/pydata/pandas/pull/4092#issuecomment-20262236
> .
 yep
 only reason to have `PandasScalar` as base class of `Timestamp`, `Period` is to distinguish these in `_is_list_like`; so you can do `isinstance(obj, PandasScalar)`,but maybe a little thin......so prob hold off on this
 if just need the instance check then can just fake with

``` python
def is_pd_scalar(obj):
    return isinstance(obj, (Timestamp, Period))
```

adding to the instance check if (when?) more scalar types are added.
 i think ok for 0.12
 :+1:  for 0.12 here as well
 @jtratner maybe squash it down a bit?
 If it's list like, use PandasContainer? Think that's already the case.
On Jul 1, 2013 7:05 AM, "jreback" notifications@github.com wrote:

> only reason to have PandasScalar as base class of Timestamp, Period is to
> distinguish these in _is_list_like; so you can do isinstance(obj,
> PandasScalar),but maybe a little thin......so prob hold off on this
> 
> —
> Reply to this email directly or view it on GitHubhttps://github.com/pydata/pandas/pull/4092#issuecomment-20275309
> .
 retract need for PandasScalar.....noneed really (and if there is legit need later, can always add)

On Jul 1, 2013, at 7:41 AM, Jeff Tratner notifications@github.com wrote:

> If it's list like, use PandasContainer? Think that's already the case. 
> On Jul 1, 2013 7:05 AM, "jreback" notifications@github.com wrote: 
> 
> > only reason to have PandasScalar as base class of Timestamp, Period is to 
> > distinguish these in _is_list_like; so you can do isinstance(obj, 
> > PandasScalar),but maybe a little thin......so prob hold off on this 
> > 
> > — 
> > Reply to this email directly or view it on GitHubhttps://github.com/pydata/pandas/pull/4092#issuecomment-20275309 
> > . 
> > 
> > —
> > Reply to this email directly or view it on GitHub.
 Yeah, I'm going to squash it down...just wanted to show steps while
considering I guess.

As an aside, it might make more sense to just create an abstract base class
(eg something that  checks that descends from PandadObject and can't
iterate)
On Jul 1, 2013 7:41 AM, "Jeffrey Tratner" jeffrey.tratner@gmail.com wrote:

> If it's list like, use PandasContainer? Think that's already the case.
> On Jul 1, 2013 7:05 AM, "jreback" notifications@github.com wrote:
> 
> > only reason to have PandasScalar as base class of Timestamp, Period is
> > to distinguish these in _is_list_like; so you can do isinstance(obj,
> > PandasScalar),but maybe a little thin......so prob hold off on this
> > 
> > —
> > Reply to this email directly or view it on GitHubhttps://github.com/pydata/pandas/pull/4092#issuecomment-20275309
> > .
 FWIW i like that you _don't_ squash for a while, while you're building, i'm starting to do that. i think it helps show the thought process. plenty of examples too, i think the series-as-ndframe pr has a ton of commits
 Plus, if you squash, it keeps the text of all the commits which is nice. For me, I like to make sure every commit passes its tests and distinct changes should end up in different commits to make it easier to localize issues if they occur. (e.g. via git bisect) 
 looks ok to merge into 0.12 - 

any objections
@wesm, @y-p 
 @cpcloud - I added the constructor argument to the baseclass and removed a
number of instances where it was erroneous.

On Mon, Jul 1, 2013 at 12:08 PM, jreback notifications@github.com wrote:

> looks ok to merge into 0.12 -
> 
> any objections
> @wesm https://github.com/wesm, @y-p https://github.com/y-p
> 
> —
> Reply to this email directly or view it on GitHubhttps://github.com/pydata/pandas/pull/4092#issuecomment-20291886
> .
 just confirming there's no user-facing API changes and have you run the perf regression test?
 @wesm there's definitely no user-facing API changes. I ran `test_perf` and it looked similar, is there a different "perf regression test"?
 nope that would be it. bombs away
 ```

Invoked with :
--ncalls: 3
--repeats: 3


-------------------------------------------------------------------------------
Test name                                    | head[ms] | base[ms] |  ratio   |
-------------------------------------------------------------------------------
frame_constructor_ndarray                    |   0.0540 |   0.0629 |   0.8586 |
series_constructor_ndarray                   |   0.0160 |   0.0173 |   0.9220 |
timeseries_slice_minutely                    |   0.0653 |   0.0707 |   0.9246 |
groupby_frame_apply_overhead                 |  13.3937 |  14.3940 |   0.9305 |
groupbym_frame_apply                         |  66.8457 |  71.7251 |   0.9320 |
ctor_index_array_string                      |   0.0637 |   0.0683 |   0.9325 |
groupby_frame_singlekey_integer              |   2.9016 |   3.1103 |   0.9329 |
groupby_frame_cython_many_columns            |   3.5630 |   3.7840 |   0.9416 |
sparse_frame_constructor                     |   7.0070 |   7.4353 |   0.9424 |
query_store_table                            |   6.6509 |   7.0089 |   0.9489 |
timeseries_add_irregular                     |  23.4577 |  24.7170 |   0.9491 |
indexing_dataframe_boolean_no_ne             |  85.8157 |  90.0673 |   0.9528 |
frame_iteritems                              |   2.6190 |   2.7456 |   0.9539 |
frame_xs_row                                 |   0.0433 |   0.0454 |   0.9545 |
timeseries_large_lookup_value                |   0.0287 |   0.0300 |   0.9550 |
read_table_multiple_date                     | 279.6036 | 291.7473 |   0.9584 |
dti_reset_index_tz                           |  17.8350 |  18.6047 |   0.9586 |
read_table_multiple_date_baseline            | 130.9160 | 136.5434 |   0.9588 |
frame_drop_dup_inplace                       |   3.5776 |   3.7280 |   0.9597 |
merge_2intkey_sort                           |  51.1840 |  53.2420 |   0.9613 |
frame_xs_col                                 |   0.0317 |   0.0330 |   0.9614 |
timeseries_asof_single                       |   0.0420 |   0.0436 |   0.9636 |
query_store_table_wide                       |  15.8637 |  16.4570 |   0.9639 |
reshape_stack_simple                         |   1.5557 |   1.6137 |   0.9640 |
frame_to_csv_mixed                           | 282.5810 | 292.7710 |   0.9652 |
reindex_fillna_pad_float32                   |   0.0827 |   0.0857 |   0.9657 |
groupby_frame_median                         |   8.6180 |   8.9057 |   0.9677 |
frame_iloc_dups                              |   0.2497 |   0.2580 |   0.9680 |
concat_series_axis1                          |  75.8933 |  78.4010 |   0.9680 |
append_frame_single_mixed                    |   1.0621 |   1.0967 |   0.9684 |
concat_small_frames                          |  19.0393 |  19.6483 |   0.9690 |
write_store_table_mixed                      | 229.4963 | 236.8270 |   0.9690 |
groupby_multi_python                         | 125.1554 | 129.0573 |   0.9698 |
groupby_apply_dict_return                    |  59.1354 |  60.9446 |   0.9703 |
frame_get_numeric_data                       |   0.1006 |   0.1036 |   0.9709 |
write_store_table_panel                      | 141.1357 | 145.1124 |   0.9726 |
frame_ctor_nested_dict_int64                 | 121.8780 | 125.2630 |   0.9730 |
indexing_panel_subset                        |   0.6837 |   0.7026 |   0.9731 |
melt_dataframe                               |   2.0859 |   2.1434 |   0.9732 |
unstack_sparse_keyspace                      |   1.8423 |   1.8926 |   0.9734 |
frame_iteritems_cached                       |   0.0884 |   0.0907 |   0.9746 |
reindex_fillna_backfill_float32              |   0.0893 |   0.0916 |   0.9748 |
dti_reset_index                              |   0.2216 |   0.2271 |   0.9762 |
timeseries_sort_index                        |  24.4863 |  25.0766 |   0.9765 |
join_dataframe_integer_key                   |   1.9927 |   2.0394 |   0.9771 |
frame_insert_500_columns                     | 131.8157 | 134.8596 |   0.9774 |
groupby_sum_booleans                         |   1.1047 |   1.1300 |   0.9776 |
frame_reindex_both_axes_ix                   |   0.4540 |   0.4640 |   0.9786 |
write_store_table                            |  96.8526 |  98.9670 |   0.9786 |
panel_from_dict_same_index                   |  33.4070 |  34.1267 |   0.9789 |
reindex_fillna_pad                           |   0.0897 |   0.0916 |   0.9792 |
timeseries_timestamp_tzinfo_cons             |   0.0190 |   0.0194 |   0.9795 |
groupby_multi_different_functions            |  18.9217 |  19.3143 |   0.9797 |
series_align_irregular_string                |  91.0884 |  92.9247 |   0.9802 |
join_dataframe_index_single_key_small        |   8.5344 |   8.7027 |   0.9807 |
groupby_series_simple_cython                 |   7.4213 |   7.5617 |   0.9814 |
sparse_series_to_frame                       | 159.4783 | 162.4194 |   0.9819 |
groupby_simple_compress_timing               |  39.7201 |  40.4267 |   0.9825 |
reindex_fillna_backfill                      |   0.0954 |   0.0970 |   0.9828 |
frame_insert_100_columns_begin               |  26.9523 |  27.4216 |   0.9829 |
join_dataframe_integer_2key                  |   6.7627 |   6.8777 |   0.9833 |
panel_from_dict_equiv_indexes                |  33.6480 |  34.2067 |   0.9837 |
timeseries_1min_5min_ohlc                    |   0.8053 |   0.8186 |   0.9837 |
write_store                                  |   7.7853 |   7.9123 |   0.9839 |
match_strings                                |   0.4560 |   0.4633 |   0.9842 |
series_ctor_from_dict                        |   3.4590 |   3.5137 |   0.9844 |
period_setitem                               | 211.7360 | 215.0184 |   0.9847 |
reindex_daterange_pad                        |   0.2046 |   0.2077 |   0.9855 |
append_frame_single_homogenous               |   0.2707 |   0.2747 |   0.9855 |
reindex_daterange_backfill                   |   0.2060 |   0.2090 |   0.9856 |
datetimeindex_normalize                      |   3.8527 |   3.9083 |   0.9858 |
stat_ops_level_frame_sum                     |   3.4913 |   3.5400 |   0.9863 |
write_store_mixed                            |  20.1573 |  20.4153 |   0.9874 |
mask_bools                                   |  18.2454 |  18.4613 |   0.9883 |
frame_repr_tall                              |   2.4837 |   2.5130 |   0.9883 |
panel_from_dict_two_different_indexes        |  57.2840 |  57.9487 |   0.9885 |
indexing_dataframe_boolean_rows              |   0.2880 |   0.2913 |   0.9885 |
frame_multi_and                              |  37.4480 |  37.8576 |   0.9892 |
timeseries_1min_5min_mean                    |   0.7963 |   0.8050 |   0.9892 |
frame_reindex_both_axes                      |   0.3664 |   0.3703 |   0.9893 |
read_store_table_panel                       |  39.2367 |  39.6434 |   0.9897 |
frame_sort_index_by_columns                  |  51.4247 |  51.9369 |   0.9901 |
frame_to_string_floats                       |  58.5093 |  59.0810 |   0.9903 |
frame_ctor_list_of_dict                      |  87.5090 |  88.3610 |   0.9904 |
indexing_dataframe_boolean_rows_object       |   0.5854 |   0.5906 |   0.9911 |
read_store                                   |   2.4203 |   2.4416 |   0.9913 |
frame_fillna_inplace                         |  12.3087 |  12.4167 |   0.9913 |
series_string_vector_slice                   | 265.6504 | 267.9363 |   0.9915 |
frame_repr_wide                              |   1.1756 |   1.1857 |   0.9916 |
frame_get_dtype_counts                       |   0.1160 |   0.1170 |   0.9918 |
stats_rank2d_axis0_average                   |  31.7893 |  32.0413 |   0.9921 |
replace_fillna                               |   2.1260 |   2.1423 |   0.9924 |
read_parse_dates_iso8601                     |   1.7130 |   1.7260 |   0.9925 |
lib_fast_zip                                 |  12.9871 |  13.0843 |   0.9926 |
stats_rank_average_int                       |  26.5594 |  26.7567 |   0.9926 |
groupby_transform                            | 173.6223 | 174.8737 |   0.9928 |
frame_ctor_nested_dict                       |  90.2743 |  90.9127 |   0.9930 |
index_datetime_intersection                  |  14.6950 |  14.7897 |   0.9936 |
groupby_multi_different_numpy_functions      |  17.4886 |  17.5977 |   0.9938 |
datetimeindex_add_offset                     |   0.2177 |   0.2190 |   0.9938 |
stats_rank2d_axis1_average                   |  21.4036 |  21.5360 |   0.9939 |
series_value_counts_int64                    |   2.7160 |   2.7327 |   0.9939 |
stats_corr_spearman                          | 104.6833 | 105.2810 |   0.9943 |
write_store_table_wide                       | 162.8940 | 163.8193 |   0.9944 |
index_datetime_union                         |  14.8407 |  14.9223 |   0.9945 |
indexing_dataframe_boolean                   |   7.7270 |   7.7680 |   0.9947 |
frame_loc_dups                               |   1.1547 |   1.1603 |   0.9951 |
read_csv_comment2                            |  30.6133 |  30.7567 |   0.9953 |
read_csv_thou_vb                             |  40.9724 |  41.1607 |   0.9954 |
read_csv_vb                                  |  28.4580 |  28.5730 |   0.9960 |
stat_ops_level_series_sum_multiple           |   9.4200 |   9.4560 |   0.9962 |
mask_floats                                  |   5.5910 |   5.6113 |   0.9964 |
frame_mult                                   |   7.3610 |   7.3800 |   0.9974 |
frame_drop_duplicates_na                     |  22.7741 |  22.8264 |   0.9977 |
indexing_dataframe_boolean_st                |  10.9363 |  10.9614 |   0.9977 |
stat_ops_level_frame_sum_multiple            |  10.9456 |  10.9647 |   0.9983 |
stats_rolling_mean                           |   1.3836 |   1.3857 |   0.9985 |
reindex_multiindex                           |   1.5523 |   1.5543 |   0.9987 |
frame_reindex_axis1                          |   4.3393 |   4.3446 |   0.9988 |
merge_2intkey_nosort                         |  22.0267 |  22.0497 |   0.9990 |
timeseries_period_downsample_mean            |  13.1647 |  13.1753 |   0.9992 |
frame_fillna_many_columns_pad                |  15.4930 |  15.5030 |   0.9994 |
lib_fast_zip_fillna                          |  18.4803 |  18.4876 |   0.9996 |
frame_boolean_row_select                     |   0.2367 |   0.2367 |   1.0000 |
series_drop_duplicates_int                   |   0.8540 |   0.8536 |   1.0005 |
index_int64_intersection                     |  27.7560 |  27.7333 |   1.0008 |
timeseries_timestamp_downsample_mean         |   8.9353 |   8.9267 |   1.0010 |
reindex_frame_level_align                    |   1.4460 |   1.4443 |   1.0012 |
frame_mult_no_ne                             |   8.2893 |   8.2797 |   1.0012 |
series_align_left_monotonic                  |  20.2010 |  20.1760 |   1.0012 |
read_store_mixed                             |   5.6214 |   5.6120 |   1.0017 |
replace_replacena                            |   2.2024 |   2.1986 |   1.0017 |
write_csv_standard                           |  60.8846 |  60.7440 |   1.0023 |
sort_level_one                               |   6.9184 |   6.9010 |   1.0025 |
timeseries_infer_freq                        |   9.5960 |   9.5716 |   1.0025 |
join_dataframe_index_single_key_bigger_sort  |  19.8517 |  19.7976 |   1.0027 |
series_align_int64_index                     |  43.9860 |  43.8654 |   1.0028 |
reshape_unstack_simple                       |   3.9103 |   3.8990 |   1.0029 |
stat_ops_level_series_sum                    |   2.6906 |   2.6813 |   1.0035 |
series_value_counts_strings                  |   6.4830 |   6.4564 |   1.0041 |
frame_multi_and_st                           |  51.8977 |  51.6740 |   1.0043 |
series_drop_duplicates_string                |   0.6460 |   0.6430 |   1.0047 |
timeseries_asof_nan                          |  12.1260 |  12.0676 |   1.0048 |
join_dataframe_index_single_key_bigger       |   9.0393 |   8.9947 |   1.0050 |
timeseries_to_datetime_iso8601               |   6.8889 |   6.8447 |   1.0065 |
frame_to_csv                                 | 193.5613 | 192.2576 |   1.0068 |
groupby_multi_size                           |  36.8676 |  36.6083 |   1.0071 |
groupby_multi_cython                         |  23.3246 |  23.1566 |   1.0073 |
write_store_table_dc                         | 222.9393 | 221.2910 |   1.0074 |
frame_to_csv2                                | 161.1224 | 159.8310 |   1.0081 |
frame_add_no_ne                              |   7.9737 |   7.9063 |   1.0085 |
stat_ops_series_std                          |   0.3087 |   0.3060 |   1.0086 |
timeseries_asof                              |  12.2716 |  12.1510 |   1.0099 |
frame_drop_duplicates                        |  24.6320 |  24.3850 |   1.0101 |
join_dataframe_index_multi                   |  26.2380 |  25.9730 |   1.0102 |
read_store_table_mixed                       |   6.4773 |   6.4117 |   1.0102 |
panel_from_dict_all_different_indexes        |  80.5343 |  79.6703 |   1.0108 |
frame_add                                    |   7.2591 |   7.1804 |   1.0110 |
groupby_last                                 |   5.1003 |   5.0430 |   1.0114 |
datetimeindex_unique                         |   0.1477 |   0.1460 |   1.0114 |
read_csv_standard                            |  15.3503 |  15.1657 |   1.0122 |
groupby_first                                |   4.4200 |   4.3623 |   1.0132 |
groupby_pivot_table                          |  27.1097 |  26.7387 |   1.0139 |
groupby_last_float32                         |   4.9826 |   4.9140 |   1.0140 |
reindex_frame_level_reindex                  |   1.3996 |   1.3803 |   1.0140 |
reshape_pivot_time_series                    | 225.6830 | 222.5023 |   1.0143 |
read_store_table                             |   3.9197 |   3.8604 |   1.0154 |
frame_add_st                                 |   8.5664 |   8.4220 |   1.0171 |
groupby_first_float32                        |   4.4951 |   4.4113 |   1.0190 |
groupby_indices                              |  10.1364 |   9.9407 |   1.0197 |
sort_level_zero                              |   6.9944 |   6.8517 |   1.0208 |
frame_reindex_columns                        |   0.4106 |   0.4020 |   1.0216 |
frame_mult_st                                |   8.6043 |   8.3633 |   1.0288 |
groupby_multi_series_op                      |  21.5487 |  20.9064 |   1.0307 |
index_int64_union                            |  87.2873 |  84.6050 |   1.0317 |
stats_rank_average                           |  35.2510 |  34.1436 |   1.0324 |
frame_reindex_axis0                          |   1.1787 |   1.1410 |   1.0331 |
frame_reindex_upcast                         |  19.1567 |  18.4720 |   1.0371 |
dataframe_reindex                            |   0.4817 |   0.4636 |   1.0389 |
frame_drop_dup_na_inplace                    |   3.5870 |   3.4497 |   1.0398 |
frame_fancy_lookup_all                       |  25.4450 |  24.3870 |   1.0434 |
frame_fancy_lookup                           |   2.3506 |   2.2329 |   1.0527 |
read_store_table_wide                        |  20.6024 |  19.5236 |   1.0553 |
frame_multi_and_no_ne                        |  89.0367 |  83.9037 |   1.0612 |
-------------------------------------------------------------------------------
Test name                                    | head[ms] | base[ms] |  ratio   |
-------------------------------------------------------------------------------

Ratio < 1.0 means the target commit is faster then the baseline.
Seed used: 1234

Target [cdbd7d4] : CLN: Move _constructor checks to PandasObject base
Base   [cdb3b2c] : Merge pull request #4091 from cpcloud/fix-share-params-grouped-hist


```

test suite above @wesm - is that what reasonably close?
 looks good

@jtratner merging UNODIR (unless otherwise directed)
