text: import numpy as np
  
  
  def train_test_split(X, y, test_ratio=0.2, seed=None):
      """数据切割"""
  
      assert X.shape[0] == y.shape[0], \
          "the size of X must be equal to the size of y"
      assert 0.0 <= test_ratio <= 1.0, \
          "test_ration must be valid"
  
      if seed:
          np.random.seed(seed)
  
      shuffled_indexed = np.random.permutation(len(X))
  
      test_size = int(len(X) * test_ratio)
      test_indexes = shuffled_indexed[:test_size]
      train_indexes = shuffled_indexed[test_size:]
  
      X_train = X[train_indexes]
      y_train = y[train_indexes]
  
      X_test = X[test_indexes]
      y_test = y[test_indexes]
  
      return X_train, X_test, y_train, y_test
  