I have the following regex:

(\ |-|\^)?[a-z\d] 

I am trying to match any sequence of alphanumeric characters, that may or may not be preceded by a , -, and may or may not be followed by a ^ and a series of digits. However, this does not produce the results that I want.

For example, the following code:

import re
r = re.findall(r'(\ |-|)?[a-z\d] (\^\d )?', '4x 5x-2445y^56')

Returns the result [('', ''), (' ', ''), ('-', '^56')], but I would expect it to return ['4x', ' 5x', '-2445y^56'].

What am I doing wrong?

CodePudding user response：

You are introducing two captured groups while trying to use optional ?, which will get returned by findall. You can make them non capture using ?: while still being able to group certain pattern together:

r = re.findall(r'[ -]?[a-z\d] (?:\^\d )?', '4x 5x-2445y^56')
r
['4x', ' 5x', '-2445y^56']