迭代器相关

基于迭代器的方式，用while循环迭代取值字符串、列表、元组、字典、集合、文件对象

def for1(l):
    l = l.__iter__()
    while True:
        try:
            print(l.__next__())
        except:
            break
l = 'abcde'
for1(l)

自定义迭代器实现range功能

def range_my(start,end,step = 1):
    while True:
        if step > 0:
            if start < end:
                yield start
                start += step
            else:
                break
        else:
            if start > end:
                yield start
                start += step
            else:
                break

g = range_my(0,5,2)

for i in g:
    print(i)