accept_language_parser.py

import re

class AcceptLanguage:
    __regex = re.compile(r";q=([\d.]+),?", re.I)
    __jail = object()

    @classmethod
    def parse(cls, string: str) -> "AcceptLanguage":
        instance = cls(cls.__jail, string)
        instance.__do_parse()
        return instance

    def __do_parse(self):
        bits = self.split()
        self.__results = {
            language: probability
            for language_set, probability in zip(bits[::2], bits[1::2])
            for language in language_set.split(",")
        }

    def __init__(self, jail, value):
        if jail is not AcceptLanguage.__jail:
            raise TypeError("Please use AcceptLanguage.parse() method instead")
        self.__string = value
        self.__results = {}

    def split(self) -> list[str]:
        return [item for item in self.__regex.split(self.__string) if item]

    def get_results(self) -> dict[str, str]:
        return self.__results

    def get_highly_likely(self):
        return max(self.__results, key=self.__results.get)
      
# Use case:

al_string = "ru-RU,ru;q=0.9,en-US;q=0.8,en;q=0.7,zh-CN;q=0.6,zh;q=0.5"

res = AcceptLanguage(al_string)
assert res.get_results() == {"ru-RU": "0.9", "ru": "0.9", "en-US": "0.8", "en": "0.7", "zh-CN": "0.6", "zh": "0.5"}
assert res.get_highly_likely() == "ru-RU"