如何实现一个python函数装饰器(Decorator)

def countdown(n):
 while n > 0:
  print('time' + str(n))
  n -= 1

print(countdown.__name__)

def log(func):
  def wrapper(*args, **kw):
    print('call %s().' % func.__name__)
    return func(*args, **kw)
  return wrapper

@log
def countdown(n):
 while n > 0:
  print('time:' + str(n))
  n -= 1

countdown(10)

print(countdown.__name__)

from functools import wraps

def log(func):
  @wraps(func)
  def wrapper(*args, **kw):
    print('call %s().' % func.__name__)
    return func(*args, **kw)
  return wrapper

@log
def countdown(n):
 while n > 0:
  print('time:' + str(n))
  n -= 1

print(countdown.__name__)

import time
from functools import wraps

def TimeCost(func):
 @wraps(func)
 def wrapper(*arg, **kwargs):
  start = time.time()
  result = func(*args, **kwargs)
  end = time.time()
  print(func.__name__, end - start)
  return result
 return wrapper

@TimeCost
def countdown(n):
 while n > 0:
  print('time:' + str(n))
  n -= 1

countdown(10000)