pure_interface.py 文件源码

def _is_empty_function(func, unwrap=False):
    """ Return True if func is considered empty.
     All functions with no return statement have an implicit return None - this is explicit in the code object.
    """
    if isinstance(func, (staticmethod, classmethod, types.MethodType)):
        func = six.get_method_function(func)
    if isinstance(func, property):
        func = property.fget
    if unwrap:
        func = _unwrap_function(func)
    try:
        code_obj = six.get_function_code(func)
    except AttributeError:
        # This callable is something else - assume it is OK.
        return True

    # quick check
    if code_obj.co_code == b'd\x00\x00S' and code_obj.co_consts[0] is None:
        return True
    if code_obj.co_code == b'd\x01\x00S' and code_obj.co_consts[1] is None:
        return True
    # convert bytes to instructions
    instructions = _get_instructions(code_obj)
    if len(instructions) < 2:
        return True  # this never happens as there is always the implicit return None which is 2 instructions
    assert instructions[-1].opname == 'RETURN_VALUE'  # returns TOS (top of stack)
    instruction = instructions[-2]
    if not (instruction.opname == 'LOAD_CONST' and code_obj.co_consts[instruction.arg] is None):  # TOS is None
        return False  # return is not None
    instructions = instructions[:-2]
    if len(instructions) == 0:
        return True
    # look for raise NotImplementedError
    if instructions[-1].opname == 'RAISE_VARARGS':
        # the thing we are raising should be the result of __call__  (instantiating exception object)
        if instructions[-2].opname == 'CALL_FUNCTION':
            for instr in instructions[:-2]:
                if instr.opname == 'LOAD_GLOBAL' and code_obj.co_names[instr.arg] == 'NotImplementedError':
                    return True

    return False