Messing around with Kaprekar's procedure.

gistfile1.py

def kaprekar(s, t=4):
    """
    Demonstrate Kaprekar's procedure and its convergence to Kaprekar's constant.
    """
    s = str(s)
    # t = 3 or 4 will converge; otherwise all bets are off.
    assert len(s) <= t
    if len(s) < t:
        s = ('0' * (t - len(s))) + s
    print s
    old = None
    new = int(''.join(sorted(s))[::-1]) - int(''.join(sorted(s)))
    while old != new:
        old = new
        s = str(new)
        if len(s) < t:
            s = ('0' * (t - len(s))) + s
        print s
        new = int(''.join(sorted(s))[::-1]) - int(''.join(sorted(s)))