一、装饰器
1、为何要用装饰器
#开放封闭原则：对修改封闭，对扩展开放
2、 什么是装饰器
装饰器他人的器具，本身可以是任意可调用对象，被装饰者也可以是任意可调用对象。 强调装饰器的原则：1 不修改被装饰对象的源代码 2 不修改被装饰对象的调用方式 装饰器的目标：在遵循1和2的前提下，为被装饰对象添加上新功能
import time
def index():
time.sleep(3)
print(‘welcome to index‘)
# index()
def wrapper(func):
start_time = time.time()
func()
stop_time = time.time()
print(‘run time is %s‘ % (stop_time - start_time))
wrapper(index)
# ================闭包实现=============================
import time
def index():
time.sleep(3)
print(‘welcome to index‘)
def timmer():
func = index # 这么写严格收到层级限制了，内部的函数无法调取，需要return返回值
def wrapper(): # 注意这里，func已经定义了等于index，就不需要写默认参数了
start_time = time.time()
func()
stop_time = time.time()
print(‘run time is %s‘ % (stop_time - start_time))
return wrapper
# wrapper=timmer() #运行timmer，得到的结果是wrapper，并且把值赋给了wrapper
# wrapper()
index = timmer() # 如上，既然可以把timmer运行的返回值赋值给warpper，那么同理也可以赋值给index
index()
####这么写没有修改源代码，也没有修改调用方式，也加上的新功能。实现了装饰器
####这么写其实是有问题的，如果又来了一个函数。这种闭包就无法实现了。解决方法如下
# ==============================================
import time
def index():
time.sleep(3)
print(‘welcome to index‘)
def home():
time.sleep(2)
print(‘welcome to home page‘)
# index()
def timmer(func):
# func=index
def wrapper(): # 注意这里，func已经定义了等于index，就不需要写默认参数了
start_time = time.time()
func()
stop_time = time.time()
print(‘run time is %s‘ % (stop_time - start_time))
return wrapper
index = timmer(index) # 给func一个index的值，最后返回的值是wrapper，我可以把它赋值给index,home同理
home = timmer(home)
index()
home()
# =================装饰器=======================
import time
def timmer(func):
# func=index
def wrapper():
start = time.time()
func()
stop = time.time()
print(‘run time is %s‘ % (stop - start))
return wrapper
@timmer # index=timmer(index) 自上而下运行，代表调用timmer 并且给timmer传值为index
def index():
time.sleep(3)
print(‘welcome to index‘)
@timmer # home=timmer(home)
def home():
time.sleep(2)
print(‘welcome to home page‘)
index()
home()
# =================被装饰器是有参函数=======================
import time
def timmer(func):
# func=index
def wrapper(name):
start = time.time()
func(name)
stop = time.time()
print(‘run time is %s‘ % (stop - start))
return wrapper
@timmer # home=timmer(home)
def home(name):
time.sleep(2)
print(‘welcome %s home ‘ % (home))
home(‘egon‘)
# ===========有参和无参混合用=======================
import time
def timmer(func):
# func=index
def wrapper(*args, **kwargs): # 闭包函数适应有参无参，各种* 传参的方式
start = time.time()
func(*args, **kwargs)
stop = time.time()
print(‘run time is %s‘ % (stop - start))
return wrapper
@timmer # index=timmer(index) 自上而下运行，代表调用timmer 并且给timmer传值为index
def index():
time.sleep(3)
print(‘welcome to index‘)
@timmer # home=timmer(home)
def home(name):
time.sleep(2)
print(‘welcome %s to home ‘ % (name))
index()
home(‘agon‘)
import time
def timmer(func):
def wrapper(*args, **kwargs):
start = time.time()
res = func(*args, **kwargs)
stop = time.time()
print(‘run time is %s‘ % (stop - start))
return res
return wrapper
@timmer # index=timmer(index)
def index():
time.sleep(3)
print(‘welcome to index‘)
return 123
@timmer # home=timmer(home)
def home(name):
time.sleep(2)
print(‘welcome %s to home page‘ % name)
# res=index() #res=wrapper()
# print(res)
res1 = home(‘egon‘) # wrapper(‘egon‘)
print(res1)
装饰器返回值
3、装饰器的使用
import time
def timmer(func):
def wrapper(*args,**kwargs):
start_time=time.time()
res=func(*args,**kwargs)
stop_time=time.time()
print(‘run time is %s‘ %(stop_time-start_time))
return res
return wrapper
@timmer
def foo():
time.sleep(3)
print(‘from foo‘)
foo()
无参装饰器
def auth(driver=‘file‘):
def auth2(func):
def wrapper(*args,**kwargs):
name=input("user: ")
pwd=input("pwd: ")
if driver == ‘file‘:
if name == ‘egon‘ and pwd == ‘123‘:
print(‘login successful‘)
res=func(*args,**kwargs)
return res
elif driver == ‘ldap‘:
print(‘ldap‘)
return wrapper
return auth2
@auth(driver=‘file‘)
def foo(name):
print(name)
foo(‘egon‘)
有参装饰器
4、装饰器语法
被装饰函数的正上方，单独一行
@deco1
@deco2
@deco3
def foo():
pass
foo=deco1(deco2(deco3(foo)))
5、加认证功能的装饰器
current_user = {‘user‘: None}
def auth(func):
def wrapper(*args, **kwargs):
if current_user[‘user‘]:
return func(*args, **kwargs)
name = input(‘name: ‘).strip()
password = input(‘password: ‘).strip()
with open(‘db.txt‘, encoding=‘utf-8‘) as f:
user_dic = eval(f.read())
if name in user_dic and password == user_dic[name]:
res = func(*args, **kwargs)
current_user[‘user‘] = name
return res
else:
print(‘user or password error‘)
return wrapper
@auth # index=auth(index) index=wrapper
def index():
print(‘from index‘)
index()
@auth
def home(name):
print(‘welcome %s‘ % name)
index() # wrapper()
home(‘egon‘)
无参版本
current_user = {‘user‘: None}
def auth(auth_type=‘file‘):
def deco(func):
def wrapper(*args, **kwargs):
if auth_type == ‘file‘:
if current_user[‘user‘]:
return func(*args, **kwargs)
name = input(‘name: ‘).strip()
password = input(‘password: ‘).strip()
with open(‘db.txt‘, encoding=‘utf-8‘) as f:
user_dic = eval(f.read())
if name in user_dic and password == user_dic[name]:
res = func(*args, **kwargs)
current_user[‘user‘] = name
return res
else:
print(‘user or password error‘)
elif auth_type == ‘mysql‘:
print(‘mysql‘)
elif auth_type == ‘ldap‘:
print(‘ldap‘)
else:
print(‘not valid auth_type‘)
return wrapper
return deco
@auth(auth_type=‘mysql‘) # @deco #index=deco(index)
def index():
print(‘from index‘)
@auth(auth_type=‘file‘)
def home(name):
print(‘welcome %s‘ % name)
index() # wrapper()
home(‘egon‘)
有参版本
6、装饰器补充：wraps
from functools import wraps
def deco(func):
@wraps(func) #加在最内层函数正上方
def wrapper(*args,**kwargs):
return func(*args,**kwargs)
return wrapper
@deco
def index():
‘‘‘哈哈哈哈‘‘‘
print(‘from index‘)
print(index.__doc__)
时间： 2024-11-05 14:39:37