Problem while trying to create python generator

Question

I am trying to learn how to use generators, so I wrote this one, but it just prints the same value all the time. Why?

I want it to generate values from 999 down to 100.

>>> def gen_a():
        a=999
        while a>99:
            yield a
            a-=1


>>> gen_a().next()
999
>>> gen_a().next()
999
>>> gen_a().next()
999

Answer 1

Because you are generating the generator over and over.

Try:

f = gen_a()
f.next()
f.next()

Answer 2

You're creating a new generator each time. Try this instead:

>>> g = gen_a()
>>> g.next()
999
>>> g.next()
998
>>> g.next()
997