在Python中,枚举和我们在对象中定义的类变量时一样的,每一个类变量就是一个枚举项,访问枚举项的方式为:类名加上类变量。
虽然这样是可以解决问题的,但是并不严谨,也不怎么安全,比如:
1、枚举类中,不应该存在key相同的枚举项(类变量)
2、不允许在类外直接修改枚举项的值
下面来看看如何实现枚举类型:
import operator class EnumValue(object): def __init__(self, parent_name, name, value): self._parent_name = parent_name self._name = name self._value = value def _parents_equal(self, other): return ( hasattr(other, '_parent_name') and self._parent_name == other._parent_name) def _check_parents_equal(self, other): if not self._parents_equal(other): raise TypeError( 'This operation is valid only for enum values of the same type') def __eq__(self, other): return self._parents_equal(other) and self._value == other._value def __ne__(self, other): return not self.__eq__(other) def __lt__(self, other): self._check_parents_equal(other) return self._value < other._value def __le__(self, other): self._check_parents_equal(other) return self._value <= other._value def __gt__(self, other): self._check_parents_equal(other) return self._value > other._value def __ge__(self, other): self._check_parents_equal(other) return self._value >= other._value def __hash__(self): return hash(self._parent_name + str(self._value)) def __repr__(self): return '{}({!r}, {!r}, {!r})'.format( self.__class__.__name__, self._parent_name, self._name, self._value) def __int__(self): return int(self._value) def __str__(self): return str(self._name) class EnumMetaclass(type): def __new__(cls, name, bases, dct): uppercased = dict((k.upper(), v) for k, v in dct.items()) new_dct = dict( name=name, _enums_by_str=dict( (k, EnumValue(name, k, v)) for k, v in uppercased.items()), _enums_by_int=dict( (v, EnumValue(name, k, v)) for k, v in uppercased.items()), ) return super(EnumMetaclass, cls).__new__(cls, name, bases, new_dct) def __getattr__(cls, name): try: return cls.__getitem__(name) except KeyError: raise AttributeError def __getitem__(cls, name): try: name = name.upper() except AttributeError: pass try: return cls._enums_by_str[name] except KeyError: return cls._enums_by_int[name] def __repr__(cls): return '{}({!r}, {})'.format( cls.__class__.__name__, cls.name, ', '.join('{}={}'.format(v._name, v._value) for v in sorted(cls._enums_by_str.values()))) def values(cls): return sorted(cls._enums_by_str.values()) def _values_comparison(cls, item, comparison_operator): """ Return a list of values such that comparison_operator(value, item) is True. """ return sorted( [v for v in cls._enums_by_str.values() if comparison_operator(v, item)]) def values_lt(cls, item): return cls._values_comparison(item, operator.lt) def values_le(cls, item): return cls._values_comparison(item, operator.le) def values_gt(cls, item): return cls._values_comparison(item, operator.gt) def values_ge(cls, item): return cls._values_comparison(item, operator.ge) def values_ne(cls, item): return cls._values_comparison(item, operator.ne) def enum_factory(name, **kwargs): return EnumMetaclass(name, (), kwargs)
Python中枚举的测试:
import unittest class EnumTestCase(unittest.TestCase): def test_repr(self): ProfileAction = enum_factory( 'ProfileAction', VIEW=1, EDIT_OWN=2, EDIT_PUBLIC=3, EDIT_FULL=4) self.assertEqual( repr(ProfileAction), "EnumMetaclass('ProfileAction', VIEW=1, EDIT_OWN=2, EDIT_PUBLIC=3, EDIT_FULL=4)") def test_value_repr(self): ProfileAction = enum_factory( 'ProfileAction', VIEW=1, EDIT_OWN=2, EDIT_PUBLIC=3, EDIT_FULL=4) self.assertEqual( repr(ProfileAction.VIEW), "EnumValue('ProfileAction', 'VIEW', 1)") def test_attribute_error(self): ProfileAction = enum_factory( 'ProfileAction', VIEW=1, EDIT_OWN=2, EDIT_PUBLIC=3, EDIT_FULL=4) with self.assertRaises(AttributeError): ProfileAction.ASDFASDF def test_cast_to_str(self): ProfileAction = enum_factory( 'ProfileAction', VIEW=1, EDIT_OWN=2, EDIT_PUBLIC=3, EDIT_FULL=4) self.assertEqual(str(ProfileAction.VIEW), 'VIEW') def test_cast_to_int(self): ProfileAction = enum_factory( 'ProfileAction', VIEW=1, EDIT_OWN=2, EDIT_PUBLIC=3, EDIT_FULL=4) self.assertEqual(int(ProfileAction.VIEW), 1) def test_access_by_str(self): ProfileAction = enum_factory( 'ProfileAction', VIEW=1, EDIT_OWN=2, EDIT_PUBLIC=3, EDIT_FULL=4) self.assertEqual(ProfileAction['VIEW'], ProfileAction.VIEW) def test_access_by_int(self): ProfileAction = enum_factory( 'ProfileAction', VIEW=1, EDIT_OWN=2, EDIT_PUBLIC=3, EDIT_FULL=4) self.assertEqual(ProfileAction[1], ProfileAction.VIEW) def test_equality(self): ProfileAction = enum_factory( 'ProfileAction', VIEW=1, EDIT_OWN=2, EDIT_PUBLIC=3, EDIT_FULL=4) self.assertEqual(ProfileAction.VIEW, ProfileAction.VIEW) self.assertEqual(ProfileAction['VIEW'], ProfileAction.VIEW) self.assertEqual(ProfileAction[1], ProfileAction.VIEW) def test_inequality(self): ProfileAction = enum_factory( 'ProfileAction', VIEW=1, EDIT_OWN=2, EDIT_PUBLIC=3, EDIT_FULL=4) self.assertNotEqual(ProfileAction.VIEW, ProfileAction.EDIT_OWN) self.assertNotEqual(ProfileAction['VIEW'], ProfileAction.EDIT_OWN) self.assertNotEqual(ProfileAction[1], ProfileAction.EDIT_OWN) DashboardAction = enum_factory( 'DashboardAction', VIEW=1, EDIT_OWN=2, EDIT_PUBLIC=3, EDIT_FULL=4) self.assertNotEqual(ProfileAction.VIEW, DashboardAction.VIEW) def test_invalid_comparison(self): ProfileAction = enum_factory( 'ProfileAction', VIEW=1, EDIT_OWN=2, EDIT_PUBLIC=3, EDIT_FULL=4) DashboardAction = enum_factory( 'DashboardAction', VIEW=1, EDIT_OWN=2, EDIT_PUBLIC=3, EDIT_FULL=4) with self.assertRaises(TypeError) as cm: ProfileAction.VIEW < DashboardAction.EDIT_OWN self.assertEqual( str(cm.exception), 'This operation is valid only for enum values of the same type') def test_values(self): ProfileAction = enum_factory( 'ProfileAction', VIEW=1, EDIT_OWN=2, EDIT_PUBLIC=3, EDIT_FULL=4) self.assertEqual( ProfileAction.values(), [ EnumValue('ProfileAction', 'VIEW', 1), EnumValue('ProfileAction', 'EDIT_OWN', 2), EnumValue('ProfileAction', 'EDIT_PUBLIC', 3), EnumValue('ProfileAction', 'EDIT_FULL', 4), ]) def test_values_lt(self): ProfileAction = enum_factory( 'ProfileAction', VIEW=1, EDIT_OWN=2, EDIT_PUBLIC=3, EDIT_FULL=4) self.assertEqual( ProfileAction.values_lt(ProfileAction.EDIT_PUBLIC), [ EnumValue('ProfileAction', 'VIEW', 1), EnumValue('ProfileAction', 'EDIT_OWN', 2), ]) def test_values_le(self): ProfileAction = enum_factory( 'ProfileAction', VIEW=1, EDIT_OWN=2, EDIT_PUBLIC=3, EDIT_FULL=4) self.assertEqual( ProfileAction.values_le(ProfileAction.EDIT_PUBLIC), [ EnumValue('ProfileAction', 'VIEW', 1), EnumValue('ProfileAction', 'EDIT_OWN', 2), EnumValue('ProfileAction', 'EDIT_PUBLIC', 3), ]) def test_values_gt(self): ProfileAction = enum_factory( 'ProfileAction', VIEW=1, EDIT_OWN=2, EDIT_PUBLIC=3, EDIT_FULL=4) self.assertEqual( ProfileAction.values_gt(ProfileAction.EDIT_PUBLIC), [ EnumValue('ProfileAction', 'EDIT_FULL', 4), ]) def test_values_ge(self): ProfileAction = enum_factory( 'ProfileAction', VIEW=1, EDIT_OWN=2, EDIT_PUBLIC=3, EDIT_FULL=4) self.assertEqual( ProfileAction.values_ge(ProfileAction.EDIT_PUBLIC), [ EnumValue('ProfileAction', 'EDIT_PUBLIC', 3), EnumValue('ProfileAction', 'EDIT_FULL', 4), ]) def test_values_ne(self): ProfileAction = enum_factory( 'ProfileAction', VIEW=1, EDIT_OWN=2, EDIT_PUBLIC=3, EDIT_FULL=4) self.assertEqual( ProfileAction.values_ne(ProfileAction.EDIT_PUBLIC), [ EnumValue('ProfileAction', 'VIEW', 1), EnumValue('ProfileAction', 'EDIT_OWN', 2), EnumValue('ProfileAction', 'EDIT_FULL', 4), ]) def test_intersection_with_same_type(self): ProfileAction = enum_factory( 'ProfileAction', VIEW=1, EDIT_OWN=2, EDIT_PUBLIC=3, EDIT_FULL=4) set_a = set([ProfileAction.VIEW, ProfileAction.EDIT_OWN]) set_b = set([ProfileAction.VIEW, ProfileAction.EDIT_PUBLIC]) self.assertEqual(set_a & set_b, set([ProfileAction.VIEW])) def test_intersection_with_different_types(self): ProfileAction = enum_factory( 'ProfileAction', VIEW=1, EDIT_OWN=2, EDIT_PUBLIC=3, EDIT_FULL=4) DashboardAction = enum_factory( 'DashboardAction', VIEW=1, EDIT_OWN=2, EDIT_PUBLIC=3, EDIT_FULL=4) set_a = set([ProfileAction.VIEW, ProfileAction.EDIT_OWN]) set_b = set([DashboardAction.VIEW, DashboardAction.EDIT_PUBLIC]) self.assertEqual(set_a & set_b, set([]))
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