迭代器就是重复地做一些事情，可以简单的理解为循环，在python中实现了__iter__方法的对象是可迭代的，实现了next()方法的对象是迭代器，这样说起来有

#!/usr/bin/env python
#coding=utf-8
class Fib:
    def __init__(self):
        self.a,self.b = 0,1
    def next(self):
        self.a,self.b = self.b,self.a+self.b
        return self.a
    def __iter__(self):
        return self
fibs = Fib()
for f in fibs:
    if f < 10000:
        print f
    else:
        break

#!/usr/bin/env python
#coding=utf-8
def fib():
    a,b = 0,1
    while 1:
        a,b = b,a+b
        yield a
for f in fib():
    if f < 10000:
        print f
    else:
        break
生成器接收参数实例：
def counter(start_at):
    count = start_at
    while True:
        print ‘before count %s‘ % count
        val = (yield count)
        print ‘after count %s, val %s‘ % (count, val)
        if val is not None:
            count = val
            print ‘sts a‘
        else:
            count += 1
            print ‘sts b‘
           
if __name__ == ‘__main__‘:
    count = counter(5)
    print ‘calling1 count.next():‘, count.next()
    print ‘calling2 count.next():‘, count.next()
    print ‘calling3 count.next():‘, count.next()
    print ‘calling4 count.next():‘, count.next()
    print ‘calling5 count.next():‘, count.next()
    print ‘-------start---------‘
    s = count.send(20)
    print ‘s‘, s
    print ‘calling count.next():‘, count.next()
    print ‘calling count.close():‘, count.close()
    print ‘calling count.next():‘, count.next()

结果：
calling1 count.next(): before count 5
5
calling2 count.next(): after count 5, val None
sts b
before count 6
6
calling3 count.next(): after count 6, val None
sts b
before count 7
7
calling4 count.next(): after count 7, val None
sts b
before count 8
8
calling5 count.next(): after count 8, val None
sts b
before count 9
9
-------start---------
after count 9, val 20
sts a
before count 20
s 20
calling count.next(): after count 20, val None
sts b
before count 21
21
calling count.close(): None
calling count.next():
Traceback (most recent call last):
  File "D:\Python27\counter.py", line 26, in <module>
    print ‘calling count.next():‘, count.next()
StopIteration