Python中的枚举类型

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：

<pre class="brush:php;toolbar:false">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)</pre>

Python中枚举的测试:

<pre class="brush:php;toolbar:false">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([]))</pre>

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