How do I format a number with a variable number of digits in Python?

Question

Say I wanted to display the number 123 with a variable number of padded zeroes on the front.

For example, if I wanted to display it in 5 digits I would have digits =

Answer 1

With the introduction of formatted string literals ("f-strings" for short) in Python 3.6, it is now possible to access previously defined variables with a briefer syntax:

>>> name = "Fred"
>>> f"He said his name is {name}."
'He said his name is Fred.'

The examples given by John La Rooy can be written as

In [1]: num=123
   ...: fill='0'
   ...: width=6
   ...: f'{num:{fill}{width}}'

Out[1]: '000123'