Python Lambda

Lambda 无法捕获循环中的临时变量，如 test01 函数的例子。如果想要捕获循环中的临时变量，可以使用 test02 闭包函数、test03 类封装、test04 partial 函数中的方式。

from functools import partial


def test01():

    def task(number):
        print('task:', id(number), number)

    func_list = []
    for number in range(10):
        print('for: ', id(number), number)
        # lambda 绑定的是局部变量的引用，而不是引用的值
        func_list.append(lambda: task(number))

    for func in func_list:
        func()


def test02():

    def wrapper(number):
        def task():
            print('task:', id(number), number)
        return task

    func_list = []
    for number in range(10):
        print('for: ', id(number), number)
        func_list.append(wrapper(number))

    for func in func_list:
        func()


def test03():

    class wrapper:

        def __init__(self, func, param):
            self.func = func
            self.param = param

        def __call__(self):
            return self.func(self.param)


    def task(number):
        print('task:', id(number), number)

    func_list = []
    for number in range(10):
        print('for: ', id(number), number)
        func_list.append(wrapper(task, number))

    for func in func_list:
        func()



def test04():

    def task(number):
        print('task:', id(number), number)

    func_list = []
    for number in range(10):
        print('for: ', id(number), number)
        func_list.append(partial(task, number))

    for func in func_list:
        func()



if __name__ == '__main__':
    # test01()
    # test02()
    # test03()
    test04()