Python: How to use re by defining an exception?

Question

This is a very newbie's question. I tried a lot on my own, but without success.

I want to use re to find numbers from a string, but with exception of the minus symbol:

>>> a1 = "25 mm"
>>> b1 = "-25 mm"
>>> c1 = "s-25"
>>> d1 = "s25-"

a = re.sub(r'\D', "", a1) gives "25", which is fine.

I would like to ask, how to use re for b1 and c1 to get "-25", and how to for d1 to get "25", because the minus symbol is behind the nummber.

Thanks for the help!

Answer 1

here you can try this one :

import re
s = re.compile(r"[+-]?\d+(?:\.\d+)?")
a1 = "25 mm"
b1 = "-25 mm"
c1 = "s-25"
d1 = "s25-"
print(s.search(d1).group(0))
print(s.search(b1).group(0))
print(s.search(c1).group(0))
print(s.search(a1).group(0))

it gives the o/p like this :

25 #d1
-25 #b1
-25 #c1
25 #a1