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# -*- encoding: latin1 -*-
# based on examples/Demo/newmetaclasses/Enum.py of the
# python distribution V2.3.
#
# Copyright for changes:
# Copyright (C) 2005 by Andreas Degert
# see LICENSE.txt in the top level distribution directory
#
"""Enumeration metaclass."""
class EnumMetaclass(type):
"Metaclass for enumeration."
def __init__(cls, name, bases, dict):
cls._members = []
cls._memberdict = {}
for attr, value in dict.items():
if not (attr.startswith('__') and attr.endswith('__')):
EnumInstance(cls, attr, value)
def __call__(cls, value):
try:
return cls._memberdict[value]
except KeyError:
raise ValueError("%s not found in enum %s" % (value, cls.__name__))
def __repr__(cls):
if cls._members:
l = [(getattr(cls, val), val) for val in cls._members]
l.sort()
s = ': {%s}' % ', '.join(["%s: %d" % (val, attr)
for attr, val in l])
else:
s = ''
return "%s%s" % (cls.__name__, s)
class EnumInstance(int):
"Class to represent an enumeration value."
def __new__(cls, classobj, enumname, value):
return int.__new__(cls, value)
def __init__(self, classobj, enumname, value):
try:
n = classobj._memberdict[value]
raise ValueError(
'Value %d found twice in Enum %s: %s, %s'
% (value, classobj.__name__, n.__enumname, enumname))
except KeyError:
pass
classobj._memberdict[value] = self
classobj._members.append(enumname)
setattr(classobj, enumname, self)
self.enumclass = classobj
self.__enumname = enumname
def __repr__(self):
return "EnumInstance(%s, %s, %d)" % (
self.enumclass.__name__, self.__enumname, self)
def __str__(self):
return "%s.%s" % (self.enumclass.__name__, self.__enumname)
class Enum:
"""Class to use as a base class for an enumeration.
class TestEnum(Enum):
a = 1
b = 2
"""
__metaclass__ = EnumMetaclass
def check_enum(value, cls, name):
if not isinstance(value, EnumInstance) or value.enumclass is not cls:
raise TypeError("%s must be a %s" % (name, cls.__name__))
if __name__ == '__main__':
class T(Enum):
a, b = range(1,3)
print T
print T.a
print T(T.a+1)
try:
print T(3)
except ValueError, e:
print e
try:
class B(Enum):
a = b = 2
print B
except ValueError, e:
print e
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