[Python][Metaprogramming] 9.1 decorator

介紹@wraps decorator

沒加@wraps

<pre class='codeblock'>#!/usr/bin/python

import time
from functools import wraps

def timethis(func):
 '''
 Decorator that reports the excution time
 '''
 #@wraps(func)
 def wrapper(*args, **kwargs):
  start = time.time()
  result = func(*args, **kwargs)
  end = time.time()
  print(func.__name__, end-start)
  return result
 return wrapper

@timethis
def countdown(n):
 '''
 Counts down
 '''
 while n > 0:
  n -= 1


countdown(10000)
print countdown.__name__
print countdown.__doc__

<\pre>

結果:

'countdown', 0.00028896331787109375) 
wrapper
None

有加@wraps

結果:

('countdown', 0.00029587745666503906) 
countdown 
Counts down

結論:

寫decorator若想保留原來的funcion __name__, __doc__那就要加 @wraps
否則就會被替換成 wrapper, None