Python装饰器

Posted 2021-01-13 corecoder

原函数

def foo():
    print(‘i am foo‘)

增加函数功能

def foo():
    print(‘i am foo‘)
    print(‘i am running‘)

不修改原函数代码的同时增加函数功能

def log(func):
    func()
    print(‘i am running‘)


def foo():
    print(‘i am foo‘)


log(foo)

函数名不变

foo = log(foo)
foo()

则需要返回一个函数

def log(func):
    def inner():
        func()
        print(‘i am running‘)
    return inner


def foo():
    print(‘i am foo‘)


foo = log(foo)
foo()

语法糖

def log(func):
    def inner():
        func()
        print(‘i am running‘)
    return inner


@log
def foo():
    print(‘i am foo‘)


foo()

原函数有参数

def log(func):
    def inner(a, b):
        func(a, b)
        print(‘i am running‘)
    return inner


@log
def foo(a, b):
    print(a, b)


foo(1, 2)

装饰器不用随着原函数的参数修改而修改

def log(func):
    def inner(*args):
        func(*args)
        print(‘i am running‘)
    return inner


@log
def foo(a, b):
    print(a, b)


foo(1, 2)

装饰器带参数

def outer(x):
    def log(func):
        def inner(*args):
            print(x)
            func(*args)
            print(‘i am running‘)
        return inner
    return log


@outer(0)
def foo(a, b):
    print(a, b)


foo(1, 2)

相当于

foo = outer(0)(foo)

函数名更正

def outer(x):
    def log(func):
        def inner(*args):
            inner.__name__ = func.__name__
            print(x)
            func(*args)
            print(‘i am running‘)
        return inner
    return log


@outer(0)
def foo(a, b):
    print(a, b)


foo(1, 2)

 更好的做法

import functools


def outer(x):
    def log(func):
        @functools.wraps(func)
        def inner(*args):
            print(x)
            func(*args)
            print(‘i am running‘)
        return inner
    return log


@outer(0)
def foo(a, b):
    print(a, b)


foo(1, 2)