How to pad zeroes to a string?

Question

What is a Pythonic way to pad a numeric string with zeroes to the left, i.e. so the numeric string has a specific length?

Answer 1

>>> '99'.zfill(5)
'00099'
>>> '99'.rjust(5,'0')
'00099'

if you want the opposite:

>>> '99'.ljust(5,'0')
'99000'