python script to go from '000' to '999'

incrpad.py

import readline, rlcompleter
readline.parse_and_bind("tab: complete")

def zeropad(n,zeros=3):
    "Pad number n with zeros. Example: zeropad(7,3) == '007'"
    nstr = str(n)
    while len(nstr) < zeros:
        nstr = "0" + nstr
    return nstr

def incr(fn=zeropad,arg=[3]):
    "Iterator that returns from '001' to '999' and beyond."
    counter = 0
    while True:
          counter = counter + 1
          yield fn(counter,*arg)

def _test_zeropad():
    assert zeropad(7) == "007" 
    assert zeropad(19) == "019" 
    assert zeropad(999) == "999" 
    assert zeropad(12345) == "12345"
    assert zeropad(1,5) == "00001" 
    return True

def _test_incr():
    i = incr()
    assert i.next() == "001"
    for x in xrange(1,901): 
        i.next()
    tested = i.next()
    assert tested == "902", tested
    return True

__all__ = [incr, zeropad]