i don't know __iter__ in python,who can give me a good code example

Question

my code run wrong

class a(object):
    def __iter(self):
        return 33
b={'a':'aaa','b':'bbb'}
c=a()
print b.itervalues()
print c.itervalues()

Please try to use the code, rather than text, because my English is not very good, thank you

Answer 1

a. Spell it right: not

   def __iter(self):

but:

   def __iter__(self):

with __ before and after iter.

b. Make the body right: not

return 33

but:

yield 33

or return iter([33])

If you return a value from __iter__, return an iterator (an iterable, as in return [33], is almost as good but not quite...); or else, yield 1+ values, making __iter__ into a generator function (so it intrinsically returns a generator iterator).

c. Call it right: not

a().itervalues()

but, e.g.:

for x in a(): print x

or

print list(a())

itervalues is a method of dict, and has nothing to do with __iter__.

If you fix all three (!) mistakes, the code works better;-).