import time

#装饰器def timer(f)  :def inner():#被装饰函数执行前  要做的事情start_time = time.time()res = f() #被装饰的函数#被装饰函数执行后  要做的事情end_time = time.time()print("函数执行时间：",end_time-start_time)return resreturn inner
@timer   #相当于  func = timer(func)   #被装饰函数def func(x,y):　　print（x+y）　　return x+y

func()

# 带参数的装饰器    可以同时控制装饰器的启用和关闭
import time
def timmer(flag):def wrapper(f):def inner(*args, **kwargs):if flag:start_time = time.time()ret = f(*args, **kwargs)end_time = time.time()print('执行时间%s' % (end_time-start_time))return retelse:ret = f(*args, **kwargs)return retreturn innerreturn wrapperflag1 = False
@timmer(flag1)  # 第一步,将@ 与后面 分开,只是单纯的执行timmer(flag1)函数     第二步 将@ 与 wrapper相结合,形成装饰器
def func1():time.sleep(0.3)print('in func1')@timmer(flag1)
def func2():time.sleep(0.3)print('in func2')@timmer(flag1)
def func3():time.sleep(0.3)print('in func3')func1()
func2()
func3()

# 做一个带参数的装饰器:
# 访问JD  JD_shop 输入京东的账号密码
# 访问taobao tianmao_shop() 输入支付宝的账号密码
status = {"username":None,"京东":False,"淘宝":False
}
def login(flag):def wapper(f):def inner(*args,**kwargs):if status[flag]:res = f(*args,**kwargs)return reselse:print("-----登录页面-------")username = input("请输入用户名：").strip()password = input("请输入密码：").strip()with open(flag,"r",encoding="utf-8") as f1:for line in f1:user,pwd  = line.strip().split("|")if user.strip() == username and password == pwd.strip():status [flag] = Trueprint("登录成功！")res = f(*args, **kwargs)return reselse:print("登录失败！")return innerreturn wapper@login('京东')
def JD():print("-----欢迎进入京东首页！------")
@login('京东')
def JD_shop():print("-----欢迎进入京东商店！------")@login('淘宝')
def taobao():print("-----欢迎进入淘宝首页！------")
@login('淘宝')
def tianmao_shop():print("-----欢迎进入天猫超市！------")JD()
JD_shop()
taobao()
tianmao_shop()

#多个装饰器 装饰一个函数def wrapper1(func):  # func == f 函数名def inner1():print('wrapper1 ,before func')  # 2
        func()print('wrapper1 ,after func')  # 4return inner1def wrapper2(func):  # func == inner1def inner2():print('wrapper2 ,before func')  # 1
        func()print('wrapper2 ,after func')  # 5return inner2# 就近原则
@wrapper2  # f = wrapper2(f) 里面f == inner1  外面的f == inner2
@wrapper1  # f = wrapper1(f) 里面的f == 函数名f   外面的f == inner1
def f():print('in f')  # 3
f()  # inner2()

#单例模式  ：只能创建同一个实例对象
class A:def __new__(cls, *args, **kwargs):print(111)obj = object.__new__(cls)return objdef __init__(self):print(222)
obj1 = A()class A:__instance = Nonedef __new__(cls, *args, **kwargs):if A.__instance is None:obj = object.__new__(cls)A.__instance = objreturn A.__instance
obj1 = A()
obj2 = A()
obj3 = A()
obj4 = A()
print(obj1)
print(obj2)
print(obj3)
print(obj4)