How to apply a python decorator to a function?
Possible Duplicate:
Understanding Python decorators
Could you please give a short code example that explains decorators?
def spam(func):
def wrapped(*args, **kwargs):
print "SPAM"
return func(*args, **kwargs)
return wrapped
@spam #this is the same as doing eggs = spam(eggs)
def eggs():
print "Eggs?"
注意你也可以使用类来编写装饰器
class Spam(object):
def __init__(self, func):
self.func = func
def __repr__(self):
return repr(self.func)
def __call__(self, *args, **kwargs):
print "SPAM"
return self.func(*args, **kwargs)
@Spam
def something():
pass
A decorator takes the function definition and creates a new function that executes this function and transforms the result.
@deco
def do():
...
is equivalent to:
do = deco(do)
Example:
def deco(func):
def inner(letter):
return func(letter).upper() #upper
return inner # return a function object
#This
@deco
def do(number):
return chr(number) # number to letter
#end
# is equivalent to this
def do2(number):
return chr(number)
do2 = deco(do2)
#end
# 65 <=> 'a'
print(do(65))
print(do2(65))
>>> B
>>> B
To understand the decorator, it is important to notice, that decorator created a new function do which is inner that executes func and transforms the result.
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