def split_data(): test_size = float(entry.get()) X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=test_size, random_state=0) huafen=(f'X_train: {X_train}, X_test: {X_test}, y_train: {y_train}, y_test: {y_test}') a6=Text(root) a6.place(x=600, y=100,height=100,width=500) a6.insert(END, huafen) return X_train, X_test, y_train, y_test label=tk.Label(root, text='请输入测试集比例：') label.place(x=600,y=65) entry=tk.Entry(root) entry.place(x=700,y=65) button = tk.Button(root, text='划分数据集', command=split_data) button.place(x=850,y=65)怎么把 X_train, X_test, y_train, y_test拿到def外面使用

可以将函数的返回值赋值给全局变量，然后在需要使用的地方直接调用即可。例如：

# 定义全局变量
global X_train, X_test, y_train, y_test

def split_data():
    # 函数内部操作
    # ...
    # 将结果赋值给全局变量
    global X_train, X_test, y_train, y_test
    X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=test_size, random_state=0)
    # ...

# 在需要使用的地方直接调用全局变量
print(X_train)
print(X_test)
print(y_train)
print(y_test)