/Demo/newmetaclasses/Enum.py
http://unladen-swallow.googlecode.com/ · Python · 177 lines · 136 code · 8 blank · 33 comment · 14 complexity · d98b2efd81d2845766343bba7465bac2 MD5 · raw file
- """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)
- for obj in cls.__mro__:
- if isinstance(obj, EnumMetaclass):
- for attr in obj._members:
- # XXX inefficient
- if not attr in cls._members:
- cls._members.append(attr)
- class EnumInstance(int):
- """Class to represent an enumeration value.
- EnumInstance('Color', 'red', 12) prints as 'Color.red' and behaves
- like the integer 12 when compared, but doesn't support arithmetic.
- XXX Should it record the actual enumeration rather than just its
- name?
- """
- def __new__(cls, classname, enumname, value):
- return int.__new__(cls, value)
- def __init__(self, classname, enumname, value):
- self.__classname = classname
- self.__enumname = enumname
- def __repr__(self):
- return "EnumInstance(%s, %s, %d)" % (self.__classname, self.__enumname,
- self)
- def __str__(self):
- return "%s.%s" % (self.__classname, self.__enumname)
- class Enum:
- __metaclass__ = EnumMetaclass
- class FullEnum:
- __metaclass__ = FullEnumMetaclass
- def _test():
- class Color(Enum):
- red = 1
- green = 2
- blue = 3
- print Color.red
- print repr(Color.red)
- print Color.red == Color.red
- print Color.red == Color.blue
- print Color.red == 1
- print Color.red == 2
- class ExtendedColor(Color):
- white = 0
- orange = 4
- yellow = 5
- purple = 6
- black = 7
- print ExtendedColor.orange
- print ExtendedColor.red
- print Color.red == ExtendedColor.red
- class OtherColor(Enum):
- white = 4
- blue = 5
- class MergedColor(Color, OtherColor):
- pass
- print MergedColor.red
- print MergedColor.white
- print Color
- print ExtendedColor
- print OtherColor
- print MergedColor
- def _test2():
- class Color(FullEnum):
- red = 1
- green = 2
- blue = 3
- print Color.red
- print repr(Color.red)
- print Color.red == Color.red
- print Color.red == Color.blue
- print Color.red == 1
- print Color.red == 2
- class ExtendedColor(Color):
- white = 0
- orange = 4
- yellow = 5
- purple = 6
- black = 7
- print ExtendedColor.orange
- print ExtendedColor.red
- print Color.red == ExtendedColor.red
- class OtherColor(FullEnum):
- white = 4
- blue = 5
- class MergedColor(Color, OtherColor):
- pass
- print MergedColor.red
- print MergedColor.white
- print Color
- print ExtendedColor
- print OtherColor
- print MergedColor
- if __name__ == '__main__':
- _test()
- _test2()