python装饰器的简单实用

装饰器(Decorators)可以实现在不变原有python 代码功能的基础上增加功能代码。

框架

def outer2(func):
    def inner(*args, **kwargs):
        func(*args, **kwargs)
    return inner


@outer2
def foo(a, b, c):
    print (a+b+c)

　　

示例一：

import time
from functools import wraps


def time_checker(func):
    @wraps(func)
    def inner(*args, **kwargs):
        time_start = time.time()
        ret = func(*args, **kwargs)
        print(f'{func.__name__} running time is {time.time() - time_start} 秒')
        return ret
    return inner


@time_checker
def func1():
    time.sleep(1)
    print(f'now func1 is  running')


if __name__ == '__main__':
    func1()

　示例二:

from functools import wraps


def logit(logfile='out.log'):
    def logging_decorator(func):
        @wraps(func)
        def wrapped_functions(*args, **kwargs):  
            log_string = func.__name__ + ' was called'
            print(log_string)
            with open(logfile, 'a') as opend_files:
                opend_files.write(log_string + '
')
            return func(*args, **kwargs)
        return wrapped_functions
    return logging_decorator


@logit
def myfunc1():
    pass

　　示例三

def outer_arg(bar):
    def outer(func):
        def inner(*args, **kwargs):
            ret = func(*args, **kwargs)
            print(bar)
            return ret
        return inner
    return outer

# 相当于 outer_arg('foo_arg')(foo)()


@outer_arg('foo_arg')
def foo(a, b, c):
    return (a+b+c)


print(foo(1,3,5))

　　示例四

class Count(object):
    def __init__(self, func):
        self._func = func
        self.num_calls = 0

    def __call__(self, *args, **kwargs):  # 模拟成函数，将类模拟成可调用的对象
        self.num_calls += 1
        print(f'num of call is {self.num_calls}')


@Count
def example():
    print('hello')

　　示例五

def decorator(aClass):
    class newClass(object):
        def __init__(self, args):
            self.times = 0
            self.wrapped = aClass(args)

        def display(self):
            # 将runtime()替换为display()
            self.times += 1
            print('run times ', self.times)
            self.wrapped.display()

    return newClass

@decorator
class MyClass(object):
    def __init__(self, number):
        self.number = number

    # 重写display
    def display(self):
        print('number is', self.number)


six = MyClass(6)
for i in range(5):
    six.display()