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"""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 list(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()
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