python yield生成器send发送数据问题，pythonyield,def countdow

python yield生成器send发送数据问题，pythonyield,def countdow

def countdown(n):    print "conunting down form" ,n    while n>=0:        print "first n:",n         newvalue=(yield n)        print "second n:",n         print "first newvalue",newvalue        if newvalue is not None:            n=newvalue        else:            n-=1        print "second newvalue",newvaluec=countdown(5)for n in c:    # print n     if n==5:        c.send(3)

输出结果：
conunting down form 5
first n: 5
second n: 5
first newvalue 3
second newvalue 3
first n: 3
second n: 3
first newvalue None
second newvalue None
first n: 2
second n: 2
first newvalue None
second newvalue None
first n: 1
second n: 1
first newvalue None
second newvalue None
first n: 0
second n: 0
first newvalue None
second newvalue None

这个期间发送的send值是不是改变了n的值，是不是会继续进行n=3的迭代？

编橙之家文章，