Python装饰器

装饰器在Python中也称为语法糖，使用到的知识点是高阶函数与闭包函数，而高阶函数的依据是Python中一切皆对象，函数也是对象，所以装饰器也是以此为依据。

def myFunc():
    l = []

    for i in range(1000000):
        l.append(i)

    return l

if __name__ == "__main__":
    myFunc()

import time


def myFunc():
    l = []

    for i in range(1000000):
        l.append(i)

    return l

if __name__ == "__main__":
    print("start...")
    start = time.time()
    myFunc()
    end = time.time()
    print("end...")
    print("execute time: %.6f" % (end - start))

import time


def myFunc():
    print("start...")
    start = time.time()

    l = []

    for i in range(1000000):
        l.append(i)

    end = time.time()
    print("end...")
    print("execute time: %.6f" % (end - start))

    return l

if __name__ == "__main__":
    myFunc()

import time


def measureTime(fun):
    def wrapped():
        print("start...")
        start = time.time()

        result = fun()

        end = time.time()
        print("end...")
        print("execute time: %.6f" % (end - start))

        return result

    return wrapped


def myFunc():
    l = []

    for i in range(1000000):
        l.append(i)

    return l

if __name__ == "__main__":
    myFunc = measureTime(myFunc)
    myFunc()

import time


def measureTime(fun):
    def wrapped():
        print("start...")
        start = time.time()

        result = fun()

        end = time.time()
        print("end...")
        print("execute time: %.6f" % (end - start))

        return result

    return wrapped


@measureTime # Python会自动执行measureTime(myFunc)，执行完之后会将结果给到myFunc，相当于myFunc = measureTime(myFunc)
def myFunc():
    l = []

    for i in range(1000000):
        l.append(i)

    return l

if __name__ == "__main__":
    yFunc()

import time


def measureTime(fun):
    def wrapped(*args, **kwargs):
        print("start...")
        start = time.time()

        result = fun(*args, **kwargs)

        end = time.time()
        print("end...")
        print("execute time: %.6f" % (end - start))

        return result

    return wrapped


@measureTime
def myFunc(num):
    l = []

    for i in range(num):
        l.append(i)

    return l

if __name__ == "__main__":
    yFunc(1000000)

import time


def measure_time(func):

    def wrapped(*args, **kwargs):
        start = time.time()

        try:
            return func(*args, **kwargs)
        finally:
            runtime = time.time() - start
            print("Execution time: %.6f seconds" % runtime)

    return wrapped


@measure_time
def f():
    l = []
    for i in range(1000000):
        l.append(i)

if __name__ == "__main__":
    f()

import logging


def wrap_func_log(level="info"):
    LOG_LEVELS = {
        "debug": logging.debug,
        "info": logging.info,
        "warning": logging.warning,
        "error": logging.error
    }
    log_command = LOG_LEVELS.get(level) or logging.info

    def dec_wrapper(func):
        def wrapper(*args, **kwargs):
            log_command(func.__name__ + " is running...")
            return func(*args, **kwargs)
        return wrapper
    return dec_wrapper


@wrap_func_log(level="error")
def add1(n):
    print(n + 1)

add1(10)

如果装饰器本身需要传入参数，则需要像下面这样处理

def log(text):
    def decorator(func):
        def wrapper(*args, **kwargs):
            print("%s %s():" % (text, func.__name__))
            return func(*args, **kwargs)
        return wrapper
    return decorator


@log("execute")
def now():
    print("2021/01/14")

装饰器的缺点是会改变原来函数的一些属性，比如__name__

import functools

def log(func):
    @functools.wraps(func)
    def wrapper(*args, **kwargs):
        print("call %s():" % func.__name__)
        return func(*args, **kwargs)
    return wrapper