Function _check_bracketed_host

Lib/urllib/parse.py:546–553

(hostname)

# Valid bracketed hosts are defined in
# https://www.rfc-editor.org/rfc/rfc3986#page-49 and https://url.spec.whatwg.org/
def _check_bracketed_host(hostname):
    if hostname.startswith('v'):
        if not re.match(r"\Av[a-fA-F0-9]+\..+\z", hostname):
            raise ValueError(f"IPvFuture address is invalid")
    else:
        ip = ipaddress.ip_address(hostname) # Throws Value Error if not IPv6 or IPv4
        if isinstance(ip, ipaddress.IPv4Address):
            raise ValueError(f"An IPv4 address cannot be in brackets")

# typed=True avoids BytesWarnings being emitted during cache key
# comparison since this API supports both bytes and str input.