Fixed width number formatting python 3

Prefix the width with a 0:

>>> '{0:03}'.format(1)
'001'

Also, you don't need the place-marker in recent versions of Python (not sure which, but at least 2.7 and 3.1):

>>> '{:03}'.format(1)
'001'

Better:

number=12
print(f'number is equal to {number:03d}')