ValueError：使用 sklearn 的 train_test_split 时

Question

我有图像和标签，我想将它们分成训练集和验证集。 我有以下相同的代码。 train_test_split保证两组数据的比例相同。

from sklearn.model_selection import train_test_split

val_split = 0.25
X_train, X_val, y_train, y_val = train_test_split(train_images, train_labels, test_size=val_split, stratify=train_labels)
X = np.concatenate((X_train, X_val))
y = np.concatenate((y_train, y_val))
y = to_categorical(y)

然后我使用 Keras 数据生成器

datagen = ImageDataGenerator(val_split)
training_generator = datagen.flow(X, y, batch_size=64,subset='training',seed=7)
validation_generator = datagen.flow(X, y, batch_size=64,subset='validation',seed=7)

但我遇到以下错误

ValueError: Training and validation subsets have different number of classes after the split. If your numpy arrays are sorted by the label, you might want to shuffle them.

我哪里错了？