Python advanced programming-part3 Decorator Prelude

Decorators are used to wrap functions, add extra functionality, and should be able to decorate a batch of functions to reduce code reuse.

a simple decorator

A function receives a function object as a parameter and returns a function object, such that a function can become a decorator, as defined below:

def deco (func): Def _deco (*args): print "Do Something" func (*args) return _deco

In the above decorator, Func is called the modified function, and some additional initialization is done before the Func is executed.

After the decorator definition is complete, use @ To modify the function, as shown here:

@deco #实际相当于执行了f = Deco (f) def f (x): Print X

After the above processing, view F's function name has become "_deco"

Print Fprint deco (f)

The operating result is:

<function _deco at 0x00000000022314a8>
<function _deco at 0x0000000002231518>

After the description finishes, F is the shallow copy version of Deco (f).

Then, when we call F ("Hello"), we get the following output:

Do something
Hello

Modifiers with parameters

Decorator is a function form, of course, you can pass in parameters, at this point, you must add a layer of nested to receive parameters, as follows:

Def deco_args (a, b):               # a,b is the parameter     def deco (func) required by the decorator:         def _deco (*args):          # * Args is the parameter required for the function being wrapped             print  "do  Something "            func (*args)               #do  something         return _deco    return deco                    #  closures are required for @deco_args ( )                     #  equivalent to F = deco_args (f) def f (x):      print x 

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Python advanced programming-part3 Decorator Prelude