10 Day Python's decorator

Decorator

1, open closed principle

Open: For adding new features is open

Closed: For modify the original function is closed

2, the role of decorators

Add new features to the original function without changing the original premise of function call

3, decorator

. 1  # ① primer - Why have decorator 
2  in order not to modify the original basis function is a function of the new functionality is added, resulting in a decorator
 . 3  
. 4  # ② simple decorator 
. 5  DEF Deco (F):
 . 6      DEF warpper () :
 7          "" " prepro function to add features " "" 
. 8          F ()
 . 9          "" " added after the original functional capabilities " "" 
10      return warpper
 . 11  
12 is  DEF FUNC ():
 13 is      Print ( ' which is the original function! ')
 14  
15 functioning = deco (function)
 16  func ()
 17  
18  #Syntactic sugar ③ decorator 
. 19  DEF Deco (F):
 20 is      DEF warpper ():
 21 is          "" " prepro function to add features " "" 
22 is          F ()
 23 is          " '" added after the original functional capabilities "" " 
24      return warpper
 25  
26 is @deco # -> where the same effect as Deco = FUNC (FUNC) 
27  DEF FUNC ():
 28      Print ( ' which is the original function ' )
 29  
30  FUNC ()
 31 is  
32  # ④ return value of decorator 
33 is  DEF Deco (F):
34     def wrapper():
35          "" " prepro function to add features " "" 
36          RES = F ()
 37 [          " '" added after the original functional capabilities "" " 
38 is          return RES
 39      return warpper
 40  
41 is  @deco
 42 is  DEF FUNC ():
 43 is      Print ( ' which is the original function ' )
 44 is  
45  FUNC ()
 46 is  
47  # ⑤ parameters with values returned decorator 
48  DEF Deco (F):
 49      DEF warpper (* args, ** kwargs):
 50          "" "Add the original function before the function "" " 
51         F = RES (* args, ** kwargs)
 52 is          "" " added after the original functional capabilities " "" 
53 is          return RES
 54 is      return warpper
 55  
56 is  @deco
 57 is  DEF FUNC (* args, ** kwargs):
 58      Print ( ' this is the original function ' )
 59  
60 FUNC (* args, ** kwargs)
 61 is  
62 is  # ⑥ multilayer decorative unit 
63 is  # TODO 
64  
65  # ⑦ is modified with a plurality of decorative function 
66  # TODO

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4, the fixed format decorator

. 1  DEF Deco (F):
 2      DEF warpper (* args, ** kwargs):
 . 3      "" " prepro function to add features " "" 
. 4      RES = F (* args, ** kwargs)
 . 5      "" " primitive function after the addition function "" " 
. 6      return RES
 . 7      return warpper
 . 8  
. 9  @deco
 10  DEF FUNC (* args, ** kwargs):
 . 11      Pring ( ' which is the original function ' )
 12 is  
13 is FUNC (* args, ** kwargs)

View Code

5, the decorator plate fixed format -wraps

If you want to use the original method under a double function, you need to call the system decorator @ wraps (func)

. 1  from functools Import Wraps
 2  
. 3  DEF Deco (FUNC):
 . 4      @wraps (FUNC) # is applied directly above the innermost function 
. 5      DEF warpper (* args, ** kwargs):
 . 6          return FUNC (* args, ** kwargs )
 . 7      return warpper
 . 8  
. 9  @deco
 10  DEF origin_func ():
 . 11      '' ' 
12 is      that the original function is a comment
 13 is      : return:
 14      ' '' 
15      Print ( ' which is the original function ' )
 16 
17  # Although the implementation of the decorator, origin_func has been pointing wrapper, but then if the @wraps (func) decorator double call method origin_func is still under the original function origin_func of 
18  Print (origin_func. __Name__ )
 19 >>> origin_func
 20 is  
21 is  Print (. origin_func the __doc__ )
 22 is >>> this is the original function of the comment
 23 is >>>: return :

View Code

6, with parameters decorator

. 1  DEF Outer (In Flag):
 2      DEF Timer (FUNC):
 . 3          DEF Inner (* args, ** kwargs):
 . 4              IF In Flag:
 . 5                  Print ( '' ' performs the functions previously done ' '' )
 . 6              Re = FUNC (* args, ** kwargs)
 . 7              IF in Flag:
 . 8                  Print ( '' ' do after the execution of the function ' '' )
 . 9              return Re
 10          return Inner
 . 11      return Timer
 12 is  
13 is  #Here first function call outer (False) -> Returns Timer -> Timer @ -> FUNC = Timer (FUNC) -> Inner FUNC = 
14  @outer (False) 
 15  DEF FUNC ():
 16      Print (111 )
 . 17  
18 is func ()

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7, a plurality of the same decorative function decorator

 1 def wrapper1(func):
 2     def inner1():
 3         print('wrapper1 ,before func')
 4         func()
 5         print('wrapper1 ,after func')
 6     return inner1
 7 
 8 def wrapper2(func):
 9     def inner2():
10         print('wrapper2 ,before func')
11         func()
12         print('wrapper2 ,after func' )
 13 is      return Inner2
 14  
15 @ wrapper2 # will inner1 decorated, i.e. inner1 = wrapper2 (inner1) = Inner2 
16 @ wrapper1 # to perform the decorator, i.e., F = wrapper1 (F) = inner1 
. 17  DEF F ():
 18 is      Print ( ' in F ' )
 . 19  
20 is  F ()
 21 is  
22 is  # result 
23 is >>> wrapper2, before FUNC
 24 >>> wrapper1, before FUNC
 25 >>> in F
 26 is >>> wrapper1, FUNC After
 27 >>> wrapper2 ,after func

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