As maybe a alternative more portable [1] and efficient [2], actually you can just use str.ljust.
In [2]: '190'.ljust(8, '0')
Out[2]: '19000000'
In [3]: str.ljust?
Docstring:
S.ljust(width[, fillchar]) -> str
Return S left-justified in a Unicode string of length width. Padding is
done using the specified fill character (default is a space).
Type: method_descriptor
[1] format is not present on old python versions. format specifier was added since Python 3.0 (see PEP 3101) and Python 2.6.
[2] reverse twice is an expensive operation.