MatchesBcp47🔗

alphanum = "[a-zA-Z0-9]"
singleton = "[0-9A-WY-Za-wy-z]"
extension = f"{singleton}(-({alphanum}){{2,8}})+"
extlang = "[a-zA-Z]{3}(-[a-zA-Z]{3}){2}"
irregular = (
    "(en-GB-oed|i-ami|i-bnn|i-default|i-enochian|i-hak|"
    "i-klingon|i-lux|i-mingo|i-navajo|i-pwn|i-tao|i-tay|"
    "i-tsu|sgn-BE-FR|sgn-BE-NL|sgn-CH-DE)"
)
regular = (
    "(art-lojban|cel-gaulish|no-bok|no-nyn|zh-guoyu|zh-hakka|"
    "zh-min|zh-min-nan|zh-xiang)"
)
grandfathered = f"({irregular}|{regular})"
language = f"([a-zA-Z]{{2,3}}(-{extlang})?|[a-zA-Z]{{4}}|[a-zA-Z]{{5,8}})"
script = "[a-zA-Z]{4}"
region = "([a-zA-Z]{2}|[0-9]{3})"
variant = f"(({alphanum}){{5,8}}|[0-9]({alphanum}){{3}})"
privateuse = f"[xX](-({alphanum}){{1,8}})+"
langtag = (
    f"{language}(-{script})?(-{region})?(-{variant})*(-{extension})*(-"
    f"{privateuse})?"
)
language_tag = f"({langtag}|{privateuse}|{grandfathered})"

pattern = f"^{language_tag}$"
return match(pattern, text) is not None