178 lines
4.3 KiB
Python
178 lines
4.3 KiB
Python
"""Enumeration metaclass."""
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class EnumMetaclass(type):
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"""Metaclass for enumeration.
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To define your own enumeration, do something like
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class Color(Enum):
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red = 1
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green = 2
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blue = 3
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Now, Color.red, Color.green and Color.blue behave totally
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different: they are enumerated values, not integers.
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Enumerations cannot be instantiated; however they can be
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subclassed.
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"""
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def __init__(cls, name, bases, dict):
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super(EnumMetaclass, cls).__init__(name, bases, dict)
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cls._members = []
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for attr in dict.keys():
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if not (attr.startswith('__') and attr.endswith('__')):
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enumval = EnumInstance(name, attr, dict[attr])
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setattr(cls, attr, enumval)
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cls._members.append(attr)
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def __getattr__(cls, name):
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if name == "__members__":
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return cls._members
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raise AttributeError(name)
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def __repr__(cls):
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s1 = s2 = ""
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enumbases = [base.__name__ for base in cls.__bases__
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if isinstance(base, EnumMetaclass) and not base is Enum]
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if enumbases:
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s1 = "(%s)" % ", ".join(enumbases)
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enumvalues = ["%s: %d" % (val, getattr(cls, val))
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for val in cls._members]
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if enumvalues:
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s2 = ": {%s}" % ", ".join(enumvalues)
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return "%s%s%s" % (cls.__name__, s1, s2)
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class FullEnumMetaclass(EnumMetaclass):
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"""Metaclass for full enumerations.
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A full enumeration displays all the values defined in base classes.
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"""
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def __init__(cls, name, bases, dict):
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super(FullEnumMetaclass, cls).__init__(name, bases, dict)
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for obj in cls.__mro__:
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if isinstance(obj, EnumMetaclass):
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for attr in obj._members:
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# XXX inefficient
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if not attr in cls._members:
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cls._members.append(attr)
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class EnumInstance(int):
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"""Class to represent an enumeration value.
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EnumInstance('Color', 'red', 12) prints as 'Color.red' and behaves
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like the integer 12 when compared, but doesn't support arithmetic.
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XXX Should it record the actual enumeration rather than just its
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name?
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"""
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def __new__(cls, classname, enumname, value):
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return int.__new__(cls, value)
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def __init__(self, classname, enumname, value):
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self.__classname = classname
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self.__enumname = enumname
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def __repr__(self):
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return "EnumInstance(%s, %s, %d)" % (self.__classname, self.__enumname,
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self)
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def __str__(self):
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return "%s.%s" % (self.__classname, self.__enumname)
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class Enum(metaclass=EnumMetaclass):
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pass
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class FullEnum(metaclass=FullEnumMetaclass):
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pass
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def _test():
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class Color(Enum):
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red = 1
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green = 2
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blue = 3
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print(Color.red)
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print(repr(Color.red))
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print(Color.red == Color.red)
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print(Color.red == Color.blue)
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print(Color.red == 1)
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print(Color.red == 2)
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class ExtendedColor(Color):
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white = 0
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orange = 4
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yellow = 5
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purple = 6
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black = 7
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print(ExtendedColor.orange)
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print(ExtendedColor.red)
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print(Color.red == ExtendedColor.red)
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class OtherColor(Enum):
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white = 4
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blue = 5
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class MergedColor(Color, OtherColor):
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pass
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print(MergedColor.red)
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print(MergedColor.white)
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print(Color)
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print(ExtendedColor)
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print(OtherColor)
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print(MergedColor)
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def _test2():
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class Color(FullEnum):
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red = 1
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green = 2
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blue = 3
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print(Color.red)
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print(repr(Color.red))
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print(Color.red == Color.red)
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print(Color.red == Color.blue)
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print(Color.red == 1)
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print(Color.red == 2)
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class ExtendedColor(Color):
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white = 0
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orange = 4
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yellow = 5
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purple = 6
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black = 7
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print(ExtendedColor.orange)
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print(ExtendedColor.red)
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print(Color.red == ExtendedColor.red)
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class OtherColor(FullEnum):
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white = 4
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blue = 5
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class MergedColor(Color, OtherColor):
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pass
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print(MergedColor.red)
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print(MergedColor.white)
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print(Color)
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print(ExtendedColor)
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print(OtherColor)
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print(MergedColor)
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if __name__ == '__main__':
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_test()
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_test2()
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