我終於弄懂了Python的裝飾器（二）
此系列文檔：
二、裝飾器的高級用法
將參數傳遞給裝飾函數
＃它不是黑魔法，只是給包裝（wrapper）傳遞參數：
def a_decorator_passing_arguments(function_to_decorate):
def a_wrapper_accepting_arguments(arg1, arg2):
print("I got args! Look: {0}, {1}".format(arg1, arg2))
function_to_decorate(arg1, arg2)
return a_wrapper_accepting_arguments
＃因為當您調用裝飾器返回的函數時，調用的包裝器（wrapper），將參數傳遞給被包裝器包裝的函數
@a_decorator_passing_arguments
def print_full_name(first_name, last_name):
print("My name is {0} {1}".format(first_name, last_name))
print_full_name("Peter", "Venkman")
# 輸出:
#I got args! Look: Peter Venkman
#My name is Peter Venkman
將參數傳遞給裝飾器
關於將參數傳遞給裝飾器本身，您怎麼認為？
因為裝飾器必須接受一個函數作為參數，所以這可能會有些彆扭。
因此，您不能將裝飾函數的參數直接傳遞給裝飾器。
在尋求解決方案之前，讓我們寫一些提醒：
＃裝飾器是普通函數
def my_decorator(func):
print("I am an ordinary function")
def wrapper():
print("I am function returned by the decorator")
func()
return wrapper
# 因此，你可以調用它，而不用 "@"
def lazy_function():
print("zzzzzzzz")
decorated_function = my_decorator(lazy_function)
#輸出: I am an ordinary function
# 它輸出了 "I am an ordinary function", 因為你只是調用了裝飾器，而沒有調用函數:
# 這裡沒有什麼神奇的地方，使用'@'
@my_decorator
def lazy_function():
print("zzzzzzzz")
#outputs: I am an ordinary function
結果一樣。
my_decorator」被調用了。
因此，當您使用時@my_decorator，您要告訴Python，通過變量來調用my_decorator標記了的函數。
def decorator_maker():
print("I make decorators! I am executed only once: "
"when you make me create a decorator.")
def my_decorator(func):
print("I am a decorator! I am executed only when you decorate a function.")
def wrapped():
print("I am the wrapper around the decorated function. "
"I am called when you call the decorated function. "
"As the wrapper, I return the RESULT of the decorated function.")
return func()
print("As the decorator, I return the wrapped function.")
return wrapped
print("As a decorator maker, I return a decorator")
return my_decorator
#讓我們新建一個裝飾器
new_decorator = decorator_maker()
#輸出:
#I make decorators! I am executed only once: when you make me create a decorator.
#As a decorator maker, I return a decorator
# 讓我們裝飾這個函數
def decorated_function():
print("I am the decorated function.")
decorated_function = new_decorator(decorated_function)
#輸出:
#I am a decorator! I am executed only when you decorate a function.
#As the decorator, I return the wrapped function
# 讓我們調用這個函數
decorated_function()
#輸出:
#I am the wrapper around the decorated function. I am called when you call the decorated function.
#As the wrapper, I return the RESULT of the decorated function.
#I am the decorated function.
毫不奇怪，跟我們前邊演示的內容一樣。
讓我們再做一次完全一樣的事情，但是這次我們跳過所有討厭的中間變量：
def decorated_function():
print("I am the decorated function.")
decorated_function = decorator_maker()(decorated_function)
#輸出:
#I make decorators! I am executed only once: when you make me create a decorator.
#As a decorator maker, I return a decorator
#I am a decorator! I am executed only when you decorate a function.
#As the decorator, I return the wrapped function.
# Finally:
decorated_function()
#輸出:
#I am the wrapper around the decorated function. I am called when you call the decorated function.
#As the wrapper, I return the RESULT of the decorated function.
#I am the decorated function.
讓我們把它變的更精簡：
@decorator_maker()
def decorated_function():
print("I am the decorated function.")
#輸出:
#I make decorators! I am executed only once: when you make me create a decorator.
#As a decorator maker, I return a decorator
#I am a decorator! I am executed only when you decorate a function.
#As the decorator, I return the wrapped function.
#最終:
decorated_function()
#輸出:
#I am the wrapper around the decorated function. I am called when you call the decorated function.
#As the wrapper, I return the RESULT of the decorated function.
#I am the decorated function.
嘿，你看到了嗎？我們使用了帶有「 @」語法的函數調用！
因此，回到帶有參數的裝飾器。
如果我們可以使用函數即時生成裝飾器，則可以將參數傳遞給該函數，對嗎？
def decorator_maker_with_arguments(decorator_arg1, decorator_arg2):
print("I make decorators! And I accept arguments: {0}, {1}".format(decorator_arg1, decorator_arg2))
def my_decorator(func):
＃這裡傳遞的參數是閉包的。
＃如果您對封包感到不舒服，可以忽略這點。
print("I am the decorator. Somehow you passed me arguments: {0}, {1}".format(decorator_arg1, decorator_arg2))
＃不要混淆裝飾器參數和函數參數！
def wrapped(function_arg1, function_arg2) :
print("I am the wrapper around the decorated function.\n"
"I can access all the variables\n"
"\t- from the decorator: {0} {1}\n"
"\t- from the function call: {2} {3}\n"
"Then I can pass them to the decorated function"
.format(decorator_arg1, decorator_arg2,
function_arg1, function_arg2))
return func(function_arg1, function_arg2)
return wrapped
return my_decorator
@decorator_maker_with_arguments("Leonard", "Sheldon")
def decorated_function_with_arguments(function_arg1, function_arg2):
print("I am the decorated function and only knows about my arguments: {0}"
" {1}".format(function_arg1, function_arg2))
decorated_function_with_arguments("Rajesh", "Howard")
#輸出:
#I make decorators! And I accept arguments: Leonard Sheldon
#I am the decorator. Somehow you passed me arguments: Leonard Sheldon
#I am the wrapper around the decorated function.
#I can access all the variables
# - from the decorator: Leonard Sheldon
# - from the function call: Rajesh Howard
#Then I can pass them to the decorated function
#I am the decorated function and only knows about my arguments: Rajesh Howard
記住它：帶參數的裝飾器，可以將變量作為參數：
c1 = "Penny"
c2 = "Leslie"
@decorator_maker_with_arguments("Leonard", c1)
def decorated_function_with_arguments(function_arg1, function_arg2):
print("I am the decorated function and only knows about my arguments:"
" {0} {1}".format(function_arg1, function_arg2))
decorated_function_with_arguments(c2, "Howard")
#輸出:
#I make decorators! And I accept arguments: Leonard Penny
#I am the decorator. Somehow you passed me arguments: Leonard Penny
#I am the wrapper around the decorated function.
#I can access all the variables
# - from the decorator: Leonard Penny
# - from the function call: Leslie Howard
#Then I can pass them to the decorated function
#I am the decorated function and only know about my arguments: Leslie Howard
如您所見，您可以像任何函數傳遞參數一樣傳遞參數給裝飾器。
您甚至可以根據需要使用*args, **kwargs。
但是請記住，裝飾器僅被調用一次，僅在Python導入腳本時。之後，您將無法動態設置參數。
當您執行「 import x」時，該函數已經被修飾，因此您無法進行任何更改。
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