Add input from list + numbers

Question

Say you have a code like this...

answer = input ()
areacode = ['302', '856', '215', '413']
if answer in areacode:
***Looking for what I would put here***

is it possible to have the users input from a list be added to numbers that would count up from 0000000 to 9999999?

Basically I want to ask the user to enter a area code and when they put the area code in, generate every possible outcome of a phone number up to the last number. EX: input is 302 so 302 + 0000000, then 302 + 0000001 all the way up to 3029999999 (I know this will take a long time)

I am using the newest version of Python.

Answer 1

for i in range(10000000):
    print(str(answer)+"{0:0=7d}".format(i))

Answer 2

Python supports arbitrarily long integers. Just iterate over all these numbers, and add them to the area code multiplied by 10,000,000:

for i in range(10000000):
    print(answercode * 10000000 + i);

EDIT:
As noted in the comments, redoing the multiplication in every iteration of the loop is wasteful, and be done only once, as the result does not change between iterations:

prefix = answercode * 10000000
for i in range(10000000):
    print(prefix + i);

Answer 3

Should work

for i in range(9999999):
        print("answer"+" "+"+"+(str(i).rjust(7, '0')))