标签：去掉 shu inf out eva bubuko rgs col 领域
闭包：1，闭：内部的函数
2，包：包含了对外部函数作用域中变量的应用
外部可以执行内部函数，并且还可以用内部函数作用域中的值
闭包的意义：返回的函数对象，不仅仅是一个函数对象，在该函数外还包裹了一层作用域，这使得，该函数无论在何处调用，优先使用自己外层包裹的作用域
def func(): n = 1 def func2(): ‘‘‘闭包‘‘‘ print("from func2:",n) return func2 f = func() print(f) f()
判断闭包函数的方法：__closure__
#判断闭包函数的方法，有cell就是闭包函数，None则不是 def func(): n = 1 def func2(): ‘‘‘闭包‘‘‘ print("from func2:",n) print(func2.__closure__) return func2 f = func() f() #非闭包函数 n = 1 def func(): def func2(): print("from func2:",n) print(func2.__closure__) return func2 f = func() f()
查看闭包的元素
def func(): n = 1 def func2(): print("from func2:",n) print(func2.__closure__) return func2 f = func() f() print(f.__closure__[0].cell_contents) #查看闭包元素
应用领域：延迟计算
from urllib.request import urlopen # res = urlopen(‘http://www.baidu.com‘).read() # print(res.decode(‘utf-8‘)) def index(url): def get(): return urlopen(url).read() return get baidu = index(‘http://www.baidu.com‘) print(baidu().decode(‘utf-8‘)) print(baidu.__closure__[0].cell_contents) #查看闭包的元素
def func(): money = 1000 def func1(): name = ‘chris‘ def func2(): print(name,money) return func2 return func1 f = func() #拿到func的内存地址 a = f() #拿到func2的内存地址 a()
装饰器的功能：在不修改原函数（代码）及其调用方式的情况下对原函数功能进行扩展
装饰器的本质：就是一个闭包函数
简单装饰器：实现函数执行时间
import time def timer(func): def inner(): start_time = time.time() func() #timer函数的参数 stop_time = time.time() print(‘run time is ‘,stop_time-start_time) return inner def func(): time.sleep(2) print("from func") func = timer(func) #拿到的是inner的内存地址 func()
第7/8可使用语法糖改进（装饰器）
import time def timer(func): def inner(): start_time = time.time() func() stop_time = time.time() print(‘run time is ‘, stop_time - start_time) return inner @timer #把整下方的函数当做参数传递，相当于implement=timer(implement) def implement(): time.sleep(2) print("from func") implement()
import time def timer(func): def inner(*args,**kwargs): start_time = time.time() res = func(*args,**kwargs) stop_time = time.time() print(‘run time is ‘, stop_time - start_time) return res return inner @timer #把整下方的函数当做参数传递，相当于implement=timer(implement) def implement(a): time.sleep(2) print("from func :%s"%a) @timer def implement2(a,b): time.sleep(0.1) print("from func:",a,b) implement(‘abcd‘) implement2(3,4)
import time def timer(func): def inner(*args,**kwargs): start_time = time.time() res = func(*args,**kwargs) stop_time = time.time() print(‘run time is ‘, stop_time - start_time) return res return inner @timer #把整下方的函数当做参数传递，相当于implement=timer(implement) def implement(a): time.sleep(0.2) print("from func :%s"%a) return ‘implement over‘ # implement(‘abc‘) print(implement(‘abc‘))
1，对外部扩展是开放的
2，对内部修改是封闭的
import time def wrapper(func): # 装饰器 def inner(*args, **kwargs): ‘‘‘函数执行之前的内容扩展‘‘‘ ret = func(*args, **kwargs) ‘‘‘函数执行之前的内容扩展‘‘‘ return ret return inner @wrapper # =====>implement=timmer(implement) def implement(): time.sleep(1) print(‘abcd‘) implement()
带参数的装饰器顾名思义就是给装饰器传参
用处：当加了很多装饰器的时候，忽然不想加装饰器了想把装饰器给去掉，但代码比较多，删起来比较麻烦，那么我们可以利用带参数的装饰器去装饰它，这就像一个开关，要的时候调用，不用的时候去掉。给装饰器里面传个参数，那么语法糖也要加括号【eg：@timer()】。在语法糖的括号内传参。我们可以用三层嵌套，弄一个标识位去标识。如下代码：
# 带参数的装饰器：（相当于开关）为了给装饰器传参 # F=True#为True时就把装饰器给加上了 F=False#为False时就把装饰器给去掉了 def outer(flag): def wrapper(func): def inner(*args,**kwargs): if flag: print(‘before‘) ret=func(*args,**kwargs) print(‘after‘) else: ret = func(*args, **kwargs) return ret return inner return wrapper @outer(F)#@wrapper def hahaha(): print(‘hahaha‘) @outer(F) def shuangwaiwai(): print(‘shuangwaiwai‘) hahaha() shuangwaiwai()
import time user_status = False def auth(func): ‘‘‘auth.txt内容为{"name":"chris","password":"123"}‘‘‘ file = ‘auth.txt‘ with open(file,‘r+‘,encoding=‘utf-8‘) as f: data = eval(f.read()) global user_status if user_status == False: user_name = input(‘username:‘).strip() pass_word = input(‘password:‘).strip() if data[‘name‘] == user_name and data[‘password‘] == pass_word: print("welcome %s".center(20,‘-‘)%user_name) user_status = True else: print("wrong username or password") # else: # print(‘无需验证‘) return func def timer(func): def inner(): start_time = time.time() func() stop_time = time.time() print(‘run time is ‘,stop_time-start_time) return inner @auth @timer def func(): time.sleep(2) print("from func") func() ‘‘‘ @auth和@timer的顺序是先执行 auth里面的认证信息，再执行timer函数中的时间 ‘’‘
def qqqxing(fun): def inner(*args,**kwargs): print(‘in qqxing: before‘) ret = fun(*args,**kwargs) print(‘in qqxing: after‘) return ret return inner def pipixia(fun): def inner(*args,**kwargs): print(‘in qqxing: before‘) ret = fun(*args,**kwargs) print(‘in qqxing: after‘) return ret return inner @qqqxing @pipixia def dapangxie(): print(‘饿了吗‘) dapangxie() ‘‘‘ @qqqxing和@pipixia的执行顺序：先执行qqqxing里面的 print(‘in qqxing: before‘)，然后跳到了pipixia里面的 print(‘in qqxing: before‘) ret = fun(*args,**kwargs) print(‘in qqxing: after‘)， 完了又回到了qqqxing里面的print(‘in qqxing: after‘)。所以就如下面的运行结果截图一样 ‘‘‘
F=False l = [] def outer(flag): def wrapper(func): l.append(func) def inner(*args,**kwargs): if flag: print(‘before‘) ret = func(*args,**kwargs) print(‘after‘) else: ret = func(*args, **kwargs) return ret return inner return wrapper @outer(F)#@wrapper def hahaha(): print(‘hahaha‘) @outer(F) def shuangwaiwai(): print(‘shuangwaiwai‘) hahaha() shuangwaiwai() print(l)
标签：去掉 shu inf out eva bubuko rgs col 领域
原文地址：https://www.cnblogs.com/chris3201/p/9008424.html
