source: trunk/essentials/dev-lang/python/Demo/newmetaclasses/Enum.py@ 3364

"""Enumeration metaclass."""

class EnumMetaclass(type):
    """Metaclass for enumeration.

    To define your own enumeration, do something like

    class Color(Enum):
        red = 1
        green = 2
        blue = 3

    Now, Color.red, Color.green and Color.blue behave totally
    different: they are enumerated values, not integers.

    Enumerations cannot be instantiated; however they can be
    subclassed.
    """

    def __init__(cls, name, bases, dict):
        super(EnumMetaclass, cls).__init__(name, bases, dict)
        cls._members = []
        for attr in dict.keys():
            if not (attr.startswith('__') and attr.endswith('__')):
                enumval = EnumInstance(name, attr, dict[attr])
                setattr(cls, attr, enumval)
                cls._members.append(attr)

    def __getattr__(cls, name):
        if name == "__members__":
            return cls._members
        raise AttributeError, name

    def __repr__(cls):
        s1 = s2 = ""
        enumbases = [base.__name__ for base in cls.__bases__
                     if isinstance(base, EnumMetaclass) and not base is Enum]
        if enumbases:
            s1 = "(%s)" % ", ".join(enumbases)
        enumvalues = ["%s: %d" % (val, getattr(cls, val))
                      for val in cls._members]
        if enumvalues:
            s2 = ": {%s}" % ", ".join(enumvalues)
        return "%s%s%s" % (cls.__name__, s1, s2)

class FullEnumMetaclass(EnumMetaclass):
    """Metaclass for full enumerations.

    A full enumeration displays all the values defined in base classes.
    """

    def __init__(cls, name, bases, dict):
        super(FullEnumMetaclass, cls).__init__(name, bases, dict)