Function to convert language list to accept-languages headers

accept_languages.py

import re
from typing import List
import operator
import decimal 
# computers can't do precise operations with floating point, which is causing us to use Decimal

def float_range(start, stop, step=0.1):
    comparison_operator = operator.gt if step > 0 else operator.lt
    start, step = decimal.Decimal(start), decimal.Decimal(str(step))
    while not comparison_operator(start, stop):
        yield start
        start += step
        
# example input: en-US, es-US, haw, fr
# example output: en-US, en;q=0.9, es-US;q=0.8, es;q=0.7, haw;q=0.5, fr;0.4
def get_accept_language_header_from_languages(languages: List[str]) -> str:
    acc_languages = []
    re_language = re.compile(r"([a-z]{1,8})-[A-z]{1,8}")
    for language in languages:
        acc_languages.append(language)
        try:
            acc_languages.append(re_language.search(language).group(1))
        except AttributeError:
            pass
    _zip = zip(acc_languages, float_range(1.0, 0.1, -0.1))
    language_headers = ",".join("{0};q={1}".format(language, priority) for language, priority in _zip)
    return language_headers.replace(";q=1", "")
if __name__ == "__main__":
    print(get_accept_language_header_from_languages(["en-US", "es-US", "haw", "fr",]))