Inserting '-' character in front of all numbers in a string

[kevinliu23]

Hey guys,

I want to be able to insert a '-' character in front of all numeric
values in a string. I want to insert the '-' character to use in
conjunction with the getopt.getopt() function.

Rigt now, I'm implementing a menu system where users will be able to
select a set of options like "2a 3ab" which corresponds to menu
choices. However, with getopt.getopt(), it'll only return what I want
if I input -2a -3ab as my string. I don't want the user have to insert
a '-' character in front of all their choices, so I was thinking of
accepting the string input first, then adding in the '-' character
myself.

So my qusetion is, how do I change:

"2a 3ab" into "-2a -3ab".

Regular expressions? :/