不同交叉验证划分方式python代码

下面是常见的三种交叉验证划分方式的Python代码实现：

1. 简单交叉验证（Hold-Out Validation）

from sklearn.model_selection import train_test_split

# X为数据特征，y为数据标签
X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.3, random_state=0)

2. K折交叉验证（K-Fold Cross Validation）

from sklearn.model_selection import KFold

# X为数据特征，y为数据标签，n_splits为折数
kf = KFold(n_splits=5, random_state=0, shuffle=True)
for train_index, test_index in kf.split(X):
    X_train, X_test = X[train_index], X[test_index]
    y_train, y_test = y[train_index], y[test_index]

3. 层次交叉验证（Stratified K-Fold Cross Validation）

from sklearn.model_selection import StratifiedKFold

# X为数据特征，y为数据标签，n_splits为折数
skf = StratifiedKFold(n_splits=5, shuffle=True, random_state=0)
for train_index, test_index in skf.split(X, y):
    X_train, X_test = X[train_index], X[test_index]
    y_train, y_test = y[train_index], y[test_index]