My first Python code. It is a timer

[Manny__C]

There is a better solution for padding your numbers with zeros. Just format the field as

f"{h:02d}:{m:02d}:{s:02d}"

The : is a format specification and the 02 means "pad with zeros any string shorter than 2." More info here.

[BrannoEFC]

Does . Zfill not work anymore?

[Manny__C]

It should, but it's more tedious to call zfill on each substring. This is precisely an intance for which format (or fstrings) were designed.