padding a number with zeroes

# beautiful and fast (if you know in advance how many to pad)
>>> "%03d" % 2 
'002'

>>> "%04d" % 22 
'0022'

for more information read the format-specification-mini-language. Thanks Sanne!

an alternative offered by nfloyd is

# if you only know at runtime how much to pad
>>> i = 4
>>> str(i).zfill(3)
'004'

or

>>> '{:07d}'.format(20)
'0000020'