python，困惑在装饰和闭合 [英] python, confused in decorate and closure

问题描述

我有一些测试代码：

def num(num):
    def deco(func):
        def wrap(*args, **kwargs):
            inputed_num = num
            return func(*args, **kwargs)
        return wrap
    return deco


@num(5)
def test(a):
    return a + inputed_num

print test(1)

运行此代码时，显示inputed_num不是已定义的错误

when run this code, I got an error shows that 'inputed_num' is not defined

我的问题是：
在wrap函数中，有没有一个闭包func可以得到'inputed_num'？

My question is: In wrap function, is there not a closure that func can got 'inputed_num' ?

无论如何，如果没有，我应该如何做到我的目标：初始化一些值，并直接在主函数中使用这个值。

Anyway, If not, how should I do to got my aim: Initialize some value, and use this value directly in the main function.

思考。

推荐答案

我的问题是：在wrap函数中，有没有一个闭包，func可以得到'inputed_num'？

My question is: In wrap function, is there not a closure that func can got 'inputed_num' ?

对不起，这不是装饰器工作的方式。在之后，函数被初始定义后应用。

Sorry, that's not the way decorators work. They get applied after the function is initially defined. By then, it's too late.

写下：

@num(5)
def test(a):
    return a + inputed_num

这相当于：

def test(a):
    return a + inputed_num

test = num(5)(test)       # note that num(5) is called after test() is defined.

为了实现您的目标，让inputed_num成为 test 的第一个参数。然后，让装饰器传递参数：

To achieve your goal, let inputed_num be the first argument to test. Then, have your decorator pass in that argument:

def num(num):
    def deco(func):
        def wrap(*args, **kwargs):
            inputed_num = num
            return func(inputed_num, *args, **kwargs)  # this line changed
        return wrap
    return deco

@num(5)
def test(inputed_num, a):                              # this line changed
    return a + inputed_num

@num(6)
def test2(inputed_num, a):
    return a + inputed_num

print test(10)   # outputs 15
print test2(10)  # outputs 16

希望为您清除一切： - ）

Hope that clears everything up for you :-)

这篇关于python，困惑在装饰和闭合的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！