Noob Question: Force input to be int?

[wd.jonsson at gmail.com]

Hello everyone!
I have a piece of code that looks like this:

if len(BuildList) > 0:
    print "The script found %d game directories:" % len(BuildList)
    print
    num = 0
    for i in BuildList:
        print str(num) +"       " + i
        num = num + 1
    print
    print "Select a build number from 0 to " + str(len(BuildList) - 1)
    buildNum = int(raw_input('Select build #> '))

    while buildNum > (len(BuildList) -1) or buildNum <= -1:
        print
        print "Error: Invalid build number!"
        print "Select a build number from 0 to " + str(len(BuildList) -
1)
        print
        buildNum = int(raw_input('Select build: '))

The problem is with the while buildNum-loop. If the user enters a
non-numeric value in the buildNum input, the scripts throws an
exception. I need to constrict the user to ONLY use integers in the
input box. How can I solve this issue?