_socket.py 文件源码

def set_custom_hostname_resolver(hostname_resolver):
    """Set a custom hostname resolver.

    By default, trio's :func:`getaddrinfo` and :func:`getnameinfo` functions
    use the standard system resolver functions. This function allows you to
    customize that behavior. The main intended use case is for testing, but it
    might also be useful for using third-party resolvers like `c-ares
    <https://c-ares.haxx.se/>`__ (though be warned that these rarely make
    perfect drop-in replacements for the system resolver). See
    :class:`trio.abc.HostnameResolver` for more details.

    Setting a custom hostname resolver affects all future calls to
    :func:`getaddrinfo` and :func:`getnameinfo` within the enclosing call to
    :func:`trio.run`. All other hostname resolution in trio is implemented in
    terms of these functions.

    Generally you should call this function just once, right at the beginning
    of your program.

    Args:
      hostname_resolver (trio.abc.HostnameResolver or None): The new custom
          hostname resolver, or None to restore the default behavior.

    Returns: 
      The previous hostname resolver (which may be None).

    """
    old = _overrides.hostname_resolver
    _overrides.hostname_resolver = hostname_resolver
    return old