title: Splitting training data with equal number rows for each classes
body: <p>I have a very large dataset of about 314554097 rows and 3 columns. The third column is the class. The dataset has two class 0 and 1. I need split the data into test and training data. To split the data I can use </p>
  
  <pre><code>from sklearn.cross_validation import train_test_split . 
  X_train, X_test, y_train, y_test = train_test_split(X, y, test_size = 0.75, random_state = 0)  
  </code></pre>
  
  <p>But, The dataset contains about 99 percent of class 0 and only 1 percent of class 1. In the training dataset, I need an equal number of class 0 and class 1 say 30000 rows of both classes. How can I do it? </p>