Question

class a(object):
    w={'a':'aaa','b':'bbb'}
    def __iter__(self):
        return iter(self.w)
    def next(self):#this is not be called
        print 'sss'
        for i in self.w:
            return i

b=a()
for i in b:
    print i

and what is Relations between __iter__ and next function.

thanks

Answer 1

I’m not entirely sure what you are asking, but the next() function isn’t called because you never explicitly call it. You define __iter__, which gets called when you do:

for i in b:

This should implicitly call the .next() method of the iterator, but the iterator isn’t a, but rather iter(self.w). As your object is not the iterator, its next() method is never called.

Hope this helps.