https://www.codewars.com/kata/55f89832ac9a66518f000118

multilinearpolynomials.py

import re

def simplify(poly):
    poly = re.findall(r'([+-])?(\d)?([a-z]+)',poly)
    poly_groups = [[group[0], ''.join(sorted(group[2]))] if group[0] == '-'
                        else ['+', ''.join(sorted(group[2]))] 
                            for group in poly 
                                for x in range(max([int(y) 
                                    for y in filter(lambda z: z.isdigit(), ['1',group[1]])]))]
    new_poly = []
    def cancelExtra():
        for i in poly_groups:
            if i[0] == '-':
                for x in poly_groups:
                    if sorted(x[1]) == sorted(i[1]) and x[0] != '-':
                        poly_groups.remove(i)
                        poly_groups.remove(x)
                        return cancelExtra()
    cancelExtra()
    simple = [[i[0], str(poly_groups.count(i)), i[1]] 
                if poly_groups.count(i) > 1 
                else [i[0], i[1]] 
                    for i in poly_groups]
    for i in simple:
        if i not in new_poly:
            new_poly.append(i)
    new_poly = ''.join([''.join(x) for x in sorted(new_poly, key=lambda x: (len(x[-1]), x[-1]))])
    return new_poly[1::] if new_poly[0] == '+' else new_poly