I was working on some SPOJ exercises when the regex module hit me with an error related to '*' being used inside the character set operator.

I looked in the module docs but it says: Special characters lose their special meaning inside sets. For example, [(+*)] will match any of the literal characters '(', '+', '*', or ')'.

Traceback attached.

Offending code (inside IDLE):
import re
a = '73479*5152'
re.match(r'(\d+)([+-*])(\d+)', a).groups()

NOTE: if I write r'(\d+)([*])(\d+)', r'(\d+)([*+-])(\d+)' or r'(\d+)([+*-])(\d+)' it works. Shouldn't it simply work as described in the docs or should the docs be updated with an entry about proper character ordering in the character class?

From re documentation:

"""Ranges of characters can be indicated by giving two characters and separating them by a '-', for example [a-z] will match any lowercase ASCII letter, [0-5][0-9] will match all the two-digits numbers from 00 to 59, and [0-9A-Fa-f] will match any hexadecimal digit. If - is escaped (e.g. [a\-z]) or if it’s placed as the first or last character (e.g. [a-]), it will match a literal '-'."""

A Python exception is not a crash. A crash is a Segmentation Fault (*nix) or 'Your program stopped unexpectedly' (Windows).

The traceback says "bad character range" because ord('+') == 43 and ord('*') == 42. It's not surprising that it complains if the range isn't valid.