Python迭代器和生成器

'''list = [1,2,3,4]
it = iter(list)
print(next(it))
print(next(it))

#for x in it:
 #   print(x,end=' ')

import sys
while True:
    try:
        print(next(it))
    except StopIteration:
        sys.exit()
'''

# 迭代器，实现__iter__,__next__
class MyNumber:
    def __iter__(self):
        self.a = 1
        return self
    def __next__(self):
        x = self.a
        self.a +=1
        return x

myclass = MyNumber()
for i in myclass:
    print(i)
    if i > 20:
        break

# 生成器，使用 yield 的函数，有yield函数即为生成器
# 每次遇到yield时，函数暂停保存信息

import sys

def fibonacci(n):
    a = 0
    b = 1
    cnt = 0

    while True:
        if(cnt > n):
            return
        yield a
        a , b = b, a + b
        cnt+=1

f = fibonacci(10)

while True:
    try:
        print(next(f), end=" ")
    except StopIteration:
        sys.exit()

还有反向迭代器__reversed__，生成器表达式，等等。