title: IndexError: list index out of range in TensorFlow
body: <p>I got an error ,IndexError: list index out of range.Traceback says</p>
  
  <pre><code>Run id: P0W5X0
  Log directory: /tmp/tflearn_logs/
  Exception in thread Thread-2:
  Traceback (most recent call last):
    File "/usr/local/Cellar/python@2/2.7.15/Frameworks/Python.framework/Versions/2.7/lib/python2.7/threading.py", line 801, in __bootstrap_inner
      self.run()
    File "/usr/local/Cellar/python@2/2.7.15/Frameworks/Python.framework/Versions/2.7/lib/python2.7/threading.py", line 754, in run
      self.__target(*self.__args, **self.__kwargs)
    File "/Users/xxx/anaconda/xxx/lib/python2.7/site-packages/tflearn/data_flow.py", line 201, in fill_batch_ids_queue
      ids = self.next_batch_ids()
    File "/Users/xxx/anaconda/xxx/lib/python2.7/site-packages/tflearn/data_flow.py", line 215, in next_batch_ids
      batch_start, batch_end = self.batches[self.batch_index]
  IndexError: list index out of range
  </code></pre>
  
  <p>I wrote codes,</p>
  
  <pre><code># coding: utf-8
  import tensorflow as tf
  import tflearn
  
  from tflearn.layers.core import input_data,dropout,fully_connected
  from tflearn.layers.conv import conv_2d, max_pool_2d
  from tflearn.layers.normalization import local_response_normalization
  from tflearn.layers.estimator import regression
  
  tf.reset_default_graph()
  net = input_data(shape=[None,20000, 4, 42])
  net = conv_2d(net, 4, 16, activation='relu')
  net = max_pool_2d(net, 1)
  net = tflearn.activations.relu(net)
  net = dropout(net, 0.5)
  net = tflearn.fully_connected(net, 2, activation='softmax')
  net = tflearn.regression(net, optimizer='adam', learning_rate=0.5, loss='categorical_crossentropy')
  
  model = tflearn.DNN(net)
  
  model.fit(np.array(trainDataSet).reshape(1,20000, 4, 42), np.array(trainLabel), n_epoch=400, batch_size=32, validation_set=0.1, show_metric=True)
  
  
  pred = np.array(model.predict(np.array(testDataSet).reshape(1,20000, 4, 42)).argmax(axis=1))
  
  label = np.array(testLabel).argmax(axis=0)
  accuracy = np.mean(pred == label, axis=0)
  
  print(accuracy)
  </code></pre>
  
  <p>I really cannot understand why such an error happens.I tried to rewrite  into</p>
  
  <pre><code>model.fit(np.array(trainDataSet).reshape(1,20000, 4, 42), np.array(trainLabel), n_epoch=400, batch_size=1, validation_set=0.1, show_metric=True) 
  </code></pre>
  
  <p>because bach causes this error,but same error happens.I rewrite another number in this part but same error happens.What is wrong in my codes?How should I fix this?</p>