Python format string

gistfile1.txt

>>> for n in range(3, 20, 3):
...     print(f'{n:2d}')
...
 3
 6
 9
12
15
18

gistfile2.txt

>>> for n in range(3, 20, 3):
...     print(f'{n:02d}')
...
03
06
09
12
15
18

see also:

• https://docs.python.org/3/tutorial/inputoutput.html#formatted-string-literals
• https://docs.python.org/3/library/string.html#format-specification-mini-language