Python 函數與常用模組 - 裝飾器(高潮)
裝飾器 - 高潮版
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
- 首頁不需要登入就可以使用
- 會員頁需要登入才能使用
- 討論區需要登入才能使用
先構思一個簡單版的。
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
def index():
print("Welcome to Index")
@auth
def home():
print("Welcome to Home")
@auth
def 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。
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
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")
@auth
def home():
print("Welcome to Home")
@auth
def bbs():
print("Welcome to BBS")
index()
home()
bbs()
---------------執行第一次結果---------------
Welcome to Index
Username:tony
Password:stark
User has passed authentication
Welcome to Home
Username:tony
Password:stark
User has passed authentication
Welcome to BBS
Process finished with exit code 0
---------------執行第二次結果---------------
Welcome to Index
Username:tony
Password:stark
User has passed authentication
Welcome to Home
Username:tony
Password:hello
Invalid 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
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
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")
@auth
def home():
print("Welcome to Home")
return "From Home"
@auth
def bbs():
print("Welcome to BBS")
index()
print(home())
bbs()
---------------執行結果---------------
Welcome to Index
Username:tony
Password:stark
User has passed authentication
Welcome to Home
None
Username:tony
Password:stark
User has passed authentication
Welcome 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？
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
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")
@auth
def home():
print("Welcome to Home")
return "From Home"
@auth
def bbs():
print("Welcome to BBS")
index()
print(home()) #wrapper()
bbs()
---------------執行結果---------------
Welcome to Index
Username:tony
Password:stark
User has passed authentication
Welcome to Home
===============after authentication===============
From Home
Username:tony
Password:stark
User has passed authentication
Welcome 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？！
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
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 <module>
@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
auth(func)修改成auth(auth_type)print("auth func:", func)修改成print("auth auth_type:", auty_type )
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
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: local
Traceback (most recent call last):
File "/Python/path/pratice_decorator4.py", line 29, in <module>
@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
def outer_wrapper():修改成def outer_wrapper(func):
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
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: local
auth auth_type: ldap
Welcome to Index
wrapper func agrs:
Username:tony
Password:stark
User has passed authentication
Welcome to Home
===============after authentication===============
From Home
wrapper func agrs:
Username:tony
Password:stark
User has passed authentication
Welcome 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
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
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)
if auth_type == "local":
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")
elif auth_type == "ldap":
print('我還不會LDAP阿~哥')
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()
