I thought no one had answered this yet lol! But hey, here's my own go at it:

    import random

    def random_alphanumeric(limit):
        #ascii alphabet of all alphanumerals
        r = (range(48,58) + range(65,91) + range(97,123))
        random.shuffle(r)
        return reduce(lambda i,s: i + chr(s),r[:random.randint(0,len(r))],"")