How to pad a numeric string with zeros to the right in Python?

Question

Python strings have a method called zfill that allows to pad a numeric string with zeros to the left.

In : str(190).zfill(8)
Out: \'00000190\'
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Answer 1

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.

Answer 2

See Format Specification Mini-Language:

In [1]: '{:<08d}'.format(190)
Out[1]: '19000000'

In [2]: '{:>08d}'.format(190)
Out[2]: '00000190'

Answer 3

Hint: The string can be inverted twice: before and after using the zfill method:

In : acc = '991000'

In : acc[::-1].zfill(9)[::-1]
Out: '991000000'

Or even more easier:

In : acc.ljust(9, '0')
Out: '991000000'