現在我們來模擬一個網站的使用者登入，透過 裝飾器 的方式來實現登入驗証功能。

條件

先構思一個簡單版的。

def index(): print("Welcome to Index")

@authdef home(): print("Welcome to Home")

@authdef bbs(): print("Welcome to BBS")

上面代碼已經完成，建立三個頁面，而且透過 @auth 裝飾器，把會員頁及討論區都有加入登入驗証的功能，接下來就來寫 @auth 這個裝飾器。

user, passwd = 'tony', 'stark'

def auth(func): def wrapper(*args, **kwargs): username = input("Username:").strip() password = input("Password:").strip()

if username == user and password == passwd: print("\033[32;1mUser has passed authentication\033[0m") func(*args, **kwargs) else: exit("\033[31;1mInvalid Username or Password\033[0m") return wrapper

def index(): print("Welcome to Index")

@authdef home(): print("Welcome to Home")

@authdef bbs(): print("Welcome to BBS")

index()home()bbs()

---------------執行第一次結果---------------Welcome to IndexUsername:tonyPassword:starkUser has passed authenticationWelcome to HomeUsername:tonyPassword:starkUser has passed authenticationWelcome to BBS

Process finished with exit code 0

---------------執行第二次結果---------------Welcome to IndexUsername:tonyPassword:starkUser has passed authenticationWelcome to HomeUsername:tonyPassword:helloInvalid Username or Password

Process finished with exit code 1

第一次測試，全部都先輸入正確的，第二次測試，故意輸入錯誤的。

看起來首頁都確實沒有做驗証就可以使用，而會員頁及討論區都需要輸入帳號密碼來驗証。

再來請觀察一下，下面的代碼

user, passwd = 'tony', 'stark'

def auth(func): def wrapper(*args, **kwargs): username = input("Username:").strip() password = input("Password:").strip()

if username == user and password == passwd: print("\033[32;1mUser has passed authentication\033[0m") func(*args, **kwargs) else: exit("\033[31;1mInvalid Username or Password\033[0m") return wrapper

def index(): print("Welcome to Index")

@authdef home(): print("Welcome to Home") return "From Home"

@authdef bbs(): print("Welcome to BBS")

index()print(home())bbs()

---------------執行結果---------------Welcome to IndexUsername:tonyPassword:starkUser has passed authenticationWelcome to HomeNoneUsername:tonyPassword:starkUser has passed authenticationWelcome to BBS

Process finished with exit code 0

有發現執行結果中，有一個 None 嗎？為什麼會有 None呢？

先前的裝飾器雖然都沒有 修改被裝飾的函數的源代碼，也沒有 修改被裝飾的函數的調用方式，但卻改變了 home函數 的結果。

這是因為 func(*args, **kwargs) 的執行結果等於是 home函數的結果，即為 From Home，所以當去調用 home()時，其實就等於去調用 wrapper函數， func(*args, **kwargs) 沒有返回，所以 home函數 的執行結果才為 None。

那這樣要怎麼修改呢？

user, passwd = 'tony', 'stark'

def auth(func): def wrapper(*args, **kwargs): username = input("Username:").strip() password = input("Password:").strip()

if username == user and password == passwd: print("\033[32;1mUser has passed authentication\033[0m") res = func(*args, **kwargs) #From home str = "after authentication" print(str.center(50, '=')) return res else: exit("\033[31;1mInvalid Username or Password\033[0m") return wrapper

def index(): print("Welcome to Index")

@authdef home(): print("Welcome to Home") return "From Home"

@authdef bbs(): print("Welcome to BBS")

index()print(home()) #wrapper()bbs()

---------------執行結果---------------

Welcome to IndexUsername:tonyPassword:starkUser has passed authenticationWelcome to Home===============after authentication===============From HomeUsername:tonyPassword:starkUser has passed authenticationWelcome to BBS===============after authentication===============

Process finished with exit code 0

嗯！看起來 home函數 的執行結果也已經被正確給返回了。

接下來要正式進入正題了，由於目前使用的認証方式是採用 local的，但一般認証的方式除了local之外，還可以透過遠端的服務來做，例如： LDAP，所以我們要來模擬一下，如果同時要做 local 及 ldap 驗証登入的話，該怎麼做呢？！

user, passwd = 'tony', 'stark'

def auth(func): print("auth func:", func) def outer_wrapper(): def wrapper(*args, **kwargs): print("wrapper func agrs:", *args, **kwargs) username = input("Username:").strip() password = input("Password:").strip()

if username == user and password == passwd: print("\033[32;1mUser has passed authentication\033[0m") res = func(*args, **kwargs) # From home str = "after authentication" print(str.center(50, '=')) return res else: exit("\033[31;1mInvalid Username or Password\033[0m")

return wrapper return outer_wrapper

def index(): print("Welcome to Index")

@auth(auth_type="local")def home(): print("Welcome to Home") return "From Home"

@auth(auth_type="ldap")def bbs(): print("Welcome to BBS")

index()print(home()) #wrapper()bbs()

---------------執行結果---------------

Traceback (most recent call last): File "/Python/path/pratice_decorator4.py", line 29, in @auth(auth_type="local")TypeError: auth() got an unexpected keyword argument 'auth_type'

Process finished with exit code 1

跟著錯誤修改，因為 auth函數需要傳入參數

user, passwd = 'tony', 'stark'

def auth(auth_type): print("auth auth_type:", auth_type) def outer_wrapper(): def wrapper(*args, **kwargs): print("wrapper func agrs:", *args, **kwargs) username = input("Username:").strip() password = input("Password:").strip()

if username == user and password == passwd: print("\033[32;1mUser has passed authentication\033[0m") res = func(*args, **kwargs) # From home str = "after authentication" print(str.center(50, '=')) return res else: exit("\033[31;1mInvalid Username or Password\033[0m")

return wrapper return outer_wrapper

def index(): print("Welcome to Index")

@auth(auth_type="local")def home(): print("Welcome to Home") return "From Home"

@auth(auth_type="ldap")def bbs(): print("Welcome to BBS")

index()print(home()) #wrapper()bbs()

---------------執行結果---------------

auth auth_type: localTraceback (most recent call last): File "/Python/path/pratice_decorator4.py", line 29, in @auth(auth_type="local")TypeError: outer_wrapper() takes 0 positional arguments but 1 was given

Process finished with exit code 1

跟著錯誤再次修改，outer_wrapper() 需要0個位置參數，但卻給了一個參數，這是因為原本的 func 被刪除了， 其實 func 就要往下一層放

user, passwd = 'tony', 'stark'

def auth(auth_type): print("auth auth_type:", auth_type) def outer_wrapper(func): def wrapper(*args, **kwargs): print("wrapper func agrs:", *args, **kwargs) username = input("Username:").strip() password = input("Password:").strip()

if username == user and password == passwd: print("\033[32;1mUser has passed authentication\033[0m") res = func(*args, **kwargs) # From home str = "after authentication" print(str.center(50, '=')) return res else: exit("\033[31;1mInvalid Username or Password\033[0m")

return wrapper return outer_wrapper

def index(): print("Welcome to Index")

@auth(auth_type="local")def home(): print("Welcome to Home") return "From Home"

@auth(auth_type="ldap")def bbs(): print("Welcome to BBS")

index()print(home()) #wrapper()bbs()

---------------執行結果---------------

auth auth_type: localauth auth_type: ldapWelcome to Indexwrapper func agrs:Username:tonyPassword:starkUser has passed authenticationWelcome to Home===============after authentication===============From Homewrapper func agrs:Username:tonyPassword:starkUser has passed authenticationWelcome to BBS===============after authentication===============

Process finished with exit code 0

其實上面代碼已經可以正常執行了，但卻還沒有加入判斷 local 或是 ldap 驗証的方法，所以再修改一下代碼