Create all possible expansions for a string containing variables

expand_vars.py

import re

def expand_vars(value, vars):
    return [vars.get(seg, [ seg ]) for seg in re.split('(\$\w+)', value)]

def join_segments(segments):
    return [reduce(lambda acc, seg: (acc[0]+seg[acc[1]%len(seg)], acc[1]/len(seg)),
            segments,
            ("", val))[0]
                for val in range(0, reduce(lambda n, seg: n * len(seg), segments, 1))]

if __name__ == '__main__':
    expanded=expand_vars("foo $bar bas $bam",
        {'$bar': ["fee", "fie", "foe"], '$bam': ["tick", "tock"]})
    joined=join_segments(expanded)
    print "\n".join(joined)