Python从入门到放弃_函数闭包_迭代器

# def func():

# print(1)
#
# print(func) #内存地址 <function func at 0x027B34B0>

# def func():
# print(1)
# a = func # 函数名当做值赋值给变量
# a()
# func()

# def func():
# # print(1)
# return '大姑娘美'
#
# def func2(msg): # mag = func
# print(msg) # msg??? func内存地址
#
# func2(func()) # 函数名可以当做参数去传递 注意点 传递函数名的时候如果+()就是在传递这个函数的返回值

# def foo():
# print(2)
# # 当函数没有写return默认返回None
# def func(msg):
# print(1)
#
# return msg
# print(func(foo)) # 函数名可以当做返回值被返回

# def foo():
# print(2)
# # 当函数没有写return默认返回None
# def func(msg):
# print(1)
#
# return msg() # 你们每天都在犯的一个问题
# print(func(foo)) # 函数名可以当做返回值被返回

# def foo():
# print(1)
# return '我是策哥'
#
# def func():
# print(2)
# print(foo()) # foo() = '我是策哥'
# return '我是军哥'
#
# def func2():
# print(3)
# print(func())
# return '我是强哥'
#
# print(func2()) # func2() = '我是强哥'

# def foo():
# print(1)
# return '我是策哥'
#
# def func():
# print(2)
# ret = foo() # foo() = '我是策哥'
# return ret
#
# def func2():
# print(3)
# msg = func()
# return msg

# print(func2())

# lst = [foo,func,func2] # 函数名可以当做元素存放在一个容器当中
# print(lst)
#
# for i in lst: # 遍历 for循环
# i()

# 总结:
# 函数名可以 当做值 去赋值给变量
# 函数名可以 当做参数传递给函数
# 函数名可以 当做函数返回值,注意:返回值不能加括号 接力的要一层一层往下传,中间断了就接不到了
# 函数名可以 当做元素存放一个容器里
#　 查看函数的内存地址　print(函数名)

# def foo():
# print('foo很痛恨func')
# return '接水'
#
# def func():
# print('让foo去接水')
# ret = foo()
# return ret + '加了点药'
#
# def func2():
# print('让func去接水')
# func()
#
# func2()

# 闭包

# def func():
# name = '宝元'
# print(name)
# func() #函数　消失了

# def func():
# def foo():
# name = '宝元'
# print(name)
# foo()
# print(foo.__closure__)
# func()

# def func():
# name = '宝元'
# def foo():
# print(name)
# foo()
# # print(foo.__closure__) # (<cell at 0x007C1370: str object at 0x007C45C0>,)
# func()

# print(func.__closure__) # None

# 闭包:1.嵌套函数,内部函数使用外部变量(非全局变量)就是闭包

# 使用函数.__closure__ 获取的内容不是None

# def func():
# name = '宝元' # 生命周期延长 常驻内存
# def foo():
# print(name)
# return foo
# ret = func() # ret == foo内存地址
# ret() # foo函数

# 好处,
# 保护这个变量不被外界修改
# 生命周期延长
# 节省开辟空间和销毁空间的时间差,提高效率

# def func(): #大门
# name = '宝元' # 生命周期延长 常驻内存
# def foo(): # 班门
# print(name)
# return foo

# ret = func()
# ret()
# func()() #func() == foo foo() func()()
# ret = func()
# ret()
# func()()

# def func():
# n = 10
# def f1():
# print(n)
# return f1
# func()()

# 应用场景

import requests
# ret = requests.get('http://www.xiaohuar.com/')
# print(ret.text)

# def get_url():
# url ='666'
# def get():
# s = 4
# print(url)
# def urls():
# print(s)
# return urls
# return get
# msg = get_url()
# msg()()

# urls = get()
# print(get()())
# 装饰器 回顾闭包

# 迭代器 在原来额基础上更新???

# 遵守迭代协议(标准):
# 只要有__iter__方法的就是可迭代对象
# 可以被for循环的就是可迭代对象

# print(dir(str)) # 查看这个类型中有什么功能 可迭代__iter__
# list
# dict
# set
# tuple

# print(s.__iter__()) # 对象 iterator 迭代器
# print(lst.__iter__())
# print(dict.__iter__({'1':2}))
# print(set.__iter__({'1',2}))
# print(tuple.__iter__(('1',2)))
# print(range.__iter__(range(0,7)))
# print(dir(int))
# print(dir(bool))

# print(s.__next__())
# print(s.__next__())
# s.__iter__() # 创建了一个迭代器 具有__iter__方法和__next__方法
# print(s.__next__())
# print(s.__next__())
# print(s.__next__())

# 迭代器不能回退
#　迭代器是惰性的
# 迭代器是一次性的

# lst = [1,2,3,4,5,6]
#
# l = lst.__iter__() # 从一个可跌代对象转换成迭代器
# print(l.__next__())
# print(l.__next__())
# print(l.__next__())
# print(l.__next__())
# print(l.__next__())
# print(l.__next__())
# print(l.__next__())

# lit = [1,2,3,4,5,6]
#
# for i in lit:
# print(i)

##########for循环的机制###########

# lst = [1,2,3,4,5]
# count = 0
# l = lst.__iter__()
# while count < len(lst):
# print(l.__next__())
# count += 1

# lst = [1,2,3,4,5,67,7]
# l = lst.__iter__()
# while True:
# try: # 异常捕获
# print(l.__next__())
# except StopIteration:
# break

# s = '123'.__iter__()
# s1 = s.__iter__()
#
# print(s1.__next__())
# print(s.__next__())

# from collections import Iterable,Iterator
#
# print(isinstance([1,2,4].__iter__(),Iterator))
# print(isinstance([1,2,4],Iterable))
#
# print(isinstance('123',Iterator))
# print(isinstance('123',Iterable))
#
# print(isinstance(123,Iterator))
# print(isinstance(123,Iterable))