Transfer from http://www.cnblogs.com/BeginMan/p/3173328.html
A decorator (Decorators)
Decorator syntax beginning with @, followed by the name of decorator functions, optional parameters.
Decorative declaration is followed by an optional parameter of the function and decorative function to be decorated, as follows:
@decorator(dec_opt_args) def func(func_args): ....
In fact, overall speaking, in fact, is a decorator function, a wrapper function for function and decorative function is called when the statement is completed, after calling a function declared after the function is replaced by a decorative decorator.
Such as:
def deco(func):
...
return func
@deco
def foo():
print 'foo'
#-----------------------------------
# Equivalent is as follows:
def deco(func):
...
return func
def foo():
print 'foo'
foo = deco(foo)
Examples are as follows:
def deco1(func):
print 'ok'
return func
@deco1
def foo():
print 'foo'
foo()
# Output --------------
#ok
#foo
#------------------
If you do not use the decorator can be as follows:
def deco1(func):
print 'ok'
return func
def foo():
print 'foo'
print foo #<function foo at 0x00AFE6F0>
foo = deco1(foo)
foo()
# Output --------------
#ok
#foo
#------------------
Under contrast between the two can be found using the decorator is so easy and flexible. Especially in the development of enterprise-class.
You can also use a plurality of decorative overlay:
def deco1(func):
print 'deco1'
return func
def deco2(func):
print 'deco2'
return func
@deco1
@deco2
def foo():
print 'foo'
foo()
# Output is as follows: -----------
#deco2
#deco1
#foo
#---------------------
Equivalent to:
@deco1 @deco2 def foo(arg):pass ---------- ----------- lower equivalent foo = deco1(deco2(foo()))
Second, there is participation, no arguments decorator
The above examples are all substantially parameters and parameter easier.
1, no-argument
@deco1
@deco2
def foo(arg):pass
---------------------
foo = deco1(deco2(foo()))
2, reference
@deco1(deco_arg) @deco2 def foo(arg):pass --------------------- foo = deco1(deco_arg)(deco2(foo()))
Back decorator to function as a parameter
Third, use
1, reflog
2, the timing logic to increase detection performance
3, adding the ability to function Affairs
Fourth, examples
from time import ctime,sleep
def deco(func):
def decoIn():
print '[%s]:%s called' %(ctime(),func.__name__)
return func
return decoIn
@deco
def foo():
pass
foo()
sleep(4)
for i in range(2):
sleep(1)
foo()
# Output is as follows: --------
#[Fri Jul 05 10:45:04 2013]:foo called
#[Fri Jul 05 10:45:09 2013]:foo called
#[Fri Jul 05 10:45:10 2013]:foo called
#------------------
Five highly recommended reading: