程式紀錄-python修飾子用法

[win...@nyps.kh.edu.tw]

class decoratorWithArgument(object):

def __init__(self, arg1, arg2, arg3):

print("__init__")

self.arg1 = arg1

self.arg2 = arg2

self.arg3 = arg3

def __call__(self, f):

print("Iinside __call__")

def wrapped_f(*args):

print("Inside wrapped_f")

print("Decorator arguments:", self.arg1, self.arg2, self.arg3)

f(*args)

print("After f(*args)")

return wrapped_f

@decoratorWithArgument("hello", "world", 42)

def sayHello(a1, a2, a3, a4):

print("sayHello arguments:", a1, a2, a3, a4)

print("After decorator")

print("Prepare to call")

sayHello("say", "hello", "argument", "list")

print("after first sayHello() call")

sayHello("a", "different", "set of", "arguments")

print("after second sayHello() call")

#先解釋這個類別

類別decoratorWithArgument繼承object

定義自己的初始化,預設要3個par並將3個par設給實體化物件的屬性

定義自己被呼叫時執行的方法,必須傳入1個function參數,呼叫__call__時return內部的

function-- wrapped_f(*args),這個函數允許輸入多個參數,此外執行被掛載的函數時相當於

執行wrapped_f時會執行剛剛傳入給__call__的function參數

#再解釋

@decoreatorWithArgument(“hello”, “world”, 42)往下

因為@decoratorWithArgument有傳入參數,所以會執行__init__做好設定後再執行__call__這

時會執行print("Iinside __call__")以及return wrapped_f,至於wrapped_f的呼叫則不會執行,

必須等到所掛載的函數真實去執行才會執行此wrapped_f

因此順序應該是

__init__

Iinside __call__

After decorator

Prepare to call

Inside wrapped_f

Decorator arguments: hello world 42

sayHello arguments: say hello argument list

After f(*args)

after first sayHello() call

Inside wrapped_f

Decorator arguments: hello world 42

sayHello arguments: a different set of arguments

After f(*args)

after second sayHello() call