title: ImportError: cannot import name '_safe_split'
body: <p>I got the following errors when I tried to use the train_test_split function. Then I tried to install scipy, but it didn't help. Does anyone know which I might be missing from the error below? Thanks! </p>
  
  <hr>
  
  <pre><code>ImportError                               Traceback (most recent call last)
  &lt;ipython-input-53-57bf27feca45&gt; in &lt;module&gt;()
        1 import numpy as np
  ----&gt; 2 from sklearn.model_selection import train_test_split
        3 
        4 X_train, X_test, y_train, y_test = train_test_split(X, Y, test_size=0.33, random_state=42)
  
  /usr/local/lib/python3.4/dist-packages/sklearn/model_selection/__init__.py in &lt;module&gt;()
       15 from ._split import check_cv
       16 
  ---&gt; 17 from ._validation import cross_val_score
       18 from ._validation import cross_val_predict
       19 from ._validation import learning_curve
  
  /usr/local/lib/python3.4/dist-packages/sklearn/model_selection/_validation.py in &lt;module&gt;()
       25 from ..utils.fixes import astype
       26 from ..utils.validation import _is_arraylike, _num_samples
  ---&gt; 27 from ..utils.metaestimators import _safe_split
       28 from ..externals.joblib import Parallel, delayed, logger
       29 from ..metrics.scorer import check_scoring
  
  ImportError: cannot import name '_safe_split'
  </code></pre>