Execution of distributive property using regex

Question

I am trying to change the order using regex, but running into a problem with alternative groups.

Example: 1a,1b,1c ABC
Output: ABC*1a,ABC*1b,ABC*1c

Example: 1a,2b ABC
Output: ABC*1a,ABC*2b

Example: 1a ABC
Output: ABC*1a

So far what I have is:

re.sub(r'((\d\W,\d\W,\d\W)|(\d\W,\d\W)|(\d\W))()(\d\W\d\W\d\W)',r'\3\*\1',string)

Any ideas on how to deal with the possible subgroups?

Answer 1

I see that the question is about regular expressions, but what as @Ronald stated using them to entirely swap the content would be rather difficult. This is an example how you could use them and combine them with python methods to achieve the results that you are looking for:

import re

def parse_string_1(str_):
    prog1 = re.compile('([\d\w]*)[\,\s]')
    prog2 = re.compile('\s(\w*)')

    constant = re.findall(prog2, str_)[0]
    multipliers = re.findall(prog1, str_)

    result = []
    for multiplier in multipliers: 
        result.append(f"{constant}*{multiplier}")
    return ','.join(result)

parse_string_1("1a,1b,1c ABC")
>>> ABC*1a,ABC*1b,ABC*1c
parse_string_1("1a,2b ABC")
>>> ABC*1a,ABC*2b
parse_string_1("1a ABC")
>>> ABC*1a

If you can leave them completely you could do this:

def parse_string_2(str_):
    result = []
    multipliers, constant = str_.split(' ')
    for multiplier in multipliers.split(','):
        result.append(f"{constant}*{multiplier}")
    return ','.join(result)

parse_string_2("1a,1b,1c ABC")
>>> ABC*1a,ABC*1b,ABC*1c
parse_string_2("1a,2b ABC")
>>> ABC*1a,ABC*2b
parse_string_2("1a ABC")
>>> ABC*1a