How to format a floating number to fixed width in Python

Question

How do I format a floating number to a fixed width with the following requirements:

1. Leading zero if n < 1
2. Add trailing decimal zero(s) to fill up f

Answer 1

In python3 the following works:

>>> v=10.4
>>> print('% 6.2f' % v)
  10.40
>>> print('% 12.1f' % v)
        10.4
>>> print('%012.1f' % v)
0000000010.4