How can I get the next string, in alphanumeric ordering, in Python?

Question

I need a simple program that given a string, returns to me the next one in the alphanumeric ordering (or just the alphabetic ordering).

f("aaa")="aab"
f("aaZ")="aba"

And so on.

Is there a function for this in one of the modules already?

Answer 1

I don't think there's a built-in function to do this. The following should work:

def next_string(s):
    strip_zs = s.rstrip('z')
    if strip_zs:
        return strip_zs[:-1] + chr(ord(strip_zs[-1]) + 1) + 'a' * (len(s) - len(strip_zs))
    else:
        return 'a' * (len(s) + 1)

Explanation: you find the last character which is not a z, increment it, and replace all of the characters after it with a's. If the entire string is z's, then return a string of all a's that is one longer.

Answer 2

Are the answers at How would you translate this from Perl to Python? sufficient? Not 100% what you're asking, but close...