train_test_split set test size before train size code example

Example 1: sklearn train test split

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

Example 2: 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