instr.py 文件源码

def const_key(obj):
    # Python implmentation of the C function _PyCode_ConstantKey()
    # of Python 3.6

    obj_type = type(obj)
    # Note: check obj_type == test_type rather than isinstance(obj, test_type)
    # to not merge instance of subtypes

    if (obj is None
        or obj is Ellipsis
            or obj_type in {int, bool, bytes, str, types.CodeType}):
        return (obj_type, obj)

    if obj_type == float:
        # all we need is to make the tuple different in either the 0.0
        # or -0.0 case from all others, just to avoid the "coercion".
        if obj == 0.0 and math.copysign(1.0, obj) < 0:
            return (obj_type, obj, None)
        else:
            return (obj_type, obj)

    if obj_type == complex:
        # For the complex case we must make complex(x, 0.)
        # different from complex(x, -0.) and complex(0., y)
        # different from complex(-0., y), for any x and y.
        # All four complex zeros must be distinguished.
        real_negzero = (obj.real == 0.0 and math.copysign(1.0, obj.real) < 0.0)
        imag_negzero = (obj.imag == 0.0 and math.copysign(1.0, obj.imag) < 0.0)

        # use True, False and None singleton as tags for the real and imag
        # sign, to make tuples different
        if real_negzero and imag_negzero:
            return (obj_type, obj, True)
        elif imag_negzero:
            return (obj_type, obj, False)
        elif real_negzero:
            return (obj_type, obj, None)
        else:
            return (obj_type, obj)

    if type(obj) == tuple:
        key = tuple(const_key(item) for item in obj)
        return (obj_type, obj, key)

    if type(obj) == frozenset:
        key = frozenset(const_key(item) for item in obj)
        return (obj_type, obj, key)

    # for other types, use the object identifier as an unique identifier
    # to ensure that they are seen as unequal.
    return (obj_type, obj, id(obj))