python_message.py 文件源码

def __new__(cls, name, bases, dictionary):
    """Custom allocation for runtime-generated class types.

    We override __new__ because this is apparently the only place
    where we can meaningfully set __slots__ on the class we're creating(?).
    (The interplay between metaclasses and slots is not very well-documented).

    Args:
      name: Name of the class (ignored, but required by the
        metaclass protocol).
      bases: Base classes of the class we're constructing.
        (Should be message.Message).  We ignore this field, but
        it's required by the metaclass protocol
      dictionary: The class dictionary of the class we're
        constructing.  dictionary[_DESCRIPTOR_KEY] must contain
        a Descriptor object describing this protocol message
        type.

    Returns:
      Newly-allocated class.
    """
    descriptor = dictionary[GeneratedProtocolMessageType._DESCRIPTOR_KEY]
    if descriptor.full_name in well_known_types.WKTBASES:
      bases += (well_known_types.WKTBASES[descriptor.full_name],)
    _AddClassAttributesForNestedExtensions(descriptor, dictionary)
    _AddSlots(descriptor, dictionary)

    superclass = super(GeneratedProtocolMessageType, cls)
    new_class = superclass.__new__(cls, name, bases, dictionary)
    return new_class