from sklearn.model_selection import train_test_split X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2) code example

Example 1: train dev test split sklearn

X_train, X_test, y_train, y_test 
    = train_test_split(X, y, test_size=0.2, random_state=1)

 X_train, X_val, y_train, y_val 
    = train_test_split(X_train, y_train, test_size=0.25, random_state=1) # 0.25 x 0.8 = 0.2

Example 2: train slipt sklearn

from sklearn.model_selection import train_test_split 

X_train, X_test, y_train, y_test = train_test_split(
    X, y, test_size=0.33, random_state=42)