Python study notes (12) decorator

import time

def show_time(f):

    def inner(a, b):
        start = time.time()
        f(a, b)
        end = time.time()
        print('spend %s' % (end - start))

    return inner


@show_time           # add = show_time(add)
def add(a, b):
    print(a + b)
    time.sleep(1)


add(3, 4)

import time
import functools


def log(func):
    @functools.wraps(func)
    def wapper():
        print('%s' % func.__name__)
        func()
    return wapper


@log
def now():
    print(time.strftime('%Y-%m-%d %H:%M:%S', time.localtime()))

2018-04-27 21:56:56
now

functools.wraps is equivalent to writing wapper.__name__ = now.__name__

Otherwise the result will be

import time
import functools


def log(func):
    # @functools.wraps(func)
    def wapper():
        print('%s' % func.__name__)
        func()
    return wapper


@log
def now():
    print(time.strftime('%Y-%m-%d %H:%M:%S', time.localtime()))


now()
print(now.__name__)

2018-04-27 21:58:32
wapper

 

The decorator passes parameters as follows

import functools

import time

def log(text):

　　def decorator(func):

　　functools.wraps(func)

　　　　def wrapper():

　　　　　　print('%s-%s' % (text, func.__name__))

　　　　　　　　func()

　　　　return wrapper

　　　　return decorator

@log('whn')      #now = log('xxx')(now)

def now():

　　print(time.strftime('%Y-%m-%d %H:%M:%S', time.localtime()))

now()

 

whn-now
2018-04-27 22:07:48