URL shortener (based on md5 alg.)

gistfile1.py

# an URL shortener
from hashlib import md5

chars = (
    'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
    'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
    'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'
)

def id_exists(id):
    """
    This is just a dummy implementation. 
    In practice, some database is queried here
    """
    return False

def short(s, min_length=5):
    x = long('0x' + md5(s).hexdigest(), 16)
    ans = []
    while x > 0:
        p = x % len(chars)
        ans.append(chars[p])
        x /= len(chars)
    ans = ''.join([str(x) for x in ans])
    max_length = len(ans)
    i = min_length
    while id_exists(ans[:i]) and i < max_length:
        i += 1
    return ans[:i]
    
if __name__ == '__main__':
    import sys
    print(short(sys.argv[1]))