Python之enum模块的使用

enum模块的作用

    enum模块定义了一个提供迭代和比较功能的枚举类型。可以用这个模块为值创建明确定义符号，而不是使用字面量整数或字符串。

1、创建枚举

import enum


class BugStatus(enum.Enum):
    new = 7
    incomplete = 6
    invalid = 5
    wont_fix = 4
    in_progress = 3
    fix_committed = 2
    fix_released = 1


print('\nMember name: {}'.format(BugStatus.wont_fix.name))
print('Member value: {}'.format(BugStatus.wont_fix.value))

运行效果

Member name: wont_fix
Member value: 4

2、枚举的迭代

import enum


class BugStatus(enum.Enum):
    new = 7
    incomplete = 6
    invalid = 5
    wont_fix = 4
    in_progress = 3
    fix_committed = 2
    fix_released = 1

for status in BugStatus:
    print('{:15} = {}'.format(status.name, status.value))

运行效果

new             = 7
incomplete      = 6
invalid         = 5
wont_fix        = 4
in_progress     = 3
fix_committed   = 2
fix_released    = 1

3、枚举比较示例（由于枚举是无序，所以不支持排序）

import enum

class BugStatus(enum.Enum):
    new = 7
    incomplete = 6
    invalid = 5
    wont_fix = 4
    in_progress = 3
    fix_committed = 2
    fix_released = 1

actual_state = BugStatus.wont_fix
desired_state = BugStatus.fix_released

print('Equality:',
      actual_state == desired_state,
      actual_state == BugStatus.wont_fix)
print('Identity:',
      actual_state is desired_state,
      actual_state is BugStatus.wont_fix)
print('Ordered by value:')
try:
    print('\n'.join('  ' + s.name for s in sorted(BugStatus)))
except TypeError as err:
    print('  Cannot sort: {}'.format(err))

运行效果

Equality: False True
Identity: False True
Ordered by value:
  Cannot sort: '<' not supported between instances of 'BugStatus' and 'BugStatus'

4、整型的枚举并且排序的示例

import enum


class BugStatus(enum.IntEnum):
    new = 7
    incomplete = 6
    invalid = 5
    wont_fix = 4
    in_progress = 3
    fix_committed = 2
    fix_released = 1


print('Ordered by value:')
print('\n'.join('  ' + s.name for s in sorted(BugStatus)))

运行效果

Ordered by value:
  fix_released
  fix_committed
  in_progress
  wont_fix
  invalid
  incomplete
  new

 5、唯一枚举的示例（有相同值的Enum成员会被处理为同一个成员对象的别名引用。）

import enum

class BugStatus(enum.Enum):
    new = 7
    incomplete = 6
    invalid = 5
    wont_fix = 4
    in_progress = 3
    fix_committed = 2
    fix_released = 1

    by_design = 4
    closed = 1

for status in BugStatus:
    print('{:15} = {}'.format(status.name, status.value))

print('\nSame: by_design is wont_fix: ',
      BugStatus.by_design is BugStatus.wont_fix)
print('Same: closed is fix_released: ',
      BugStatus.closed is BugStatus.fix_released)

运行效果

new             = 7
incomplete      = 6
invalid         = 5
wont_fix        = 4
in_progress     = 3
fix_committed   = 2
fix_released    = 1

Same: by_design is wont_fix:  True
Same: closed is fix_released:  True

6、利用装饰器控制唯一枚举的示例

import enum

@enum.unique
class BugStatus(enum.Enum):
    new = 7
    incomplete = 6
    invalid = 5
    wont_fix = 4
    in_progress = 3
    fix_committed = 2
    fix_released = 1

    by_design = 4
    closed = 1

运行效果

ValueError: duplicate values found in <enum 'BugStatus'>: by_design -> wont_fix, closed -> fix_released

7、通过构造函数传入name为空格隔开创建枚举的示例

import enum

BugStatus = enum.Enum(
    value='BugStatus',
    names=('fix_released fix_committed in_progress wont_fix invalid incomplete new')
)

print('Member: {}'.format(BugStatus.new))

print('\nAll members:')
for status in BugStatus:
    print('{:15} = {}'.format(status.name, status.value))

运行效果

Member: BugStatus.new

All members:
fix_released    = 1
fix_committed   = 2
in_progress     = 3
wont_fix        = 4
invalid         = 5
incomplete      = 6
new             = 7

8、通过构造函数传入name为列表套元组的key-value创建枚举的示例

运行效果

All members:
new             = 7
incomplete      = 6
invalid         = 5
wont_fix        = 4
in_progress     = 3
fix_committed   = 2
fix_released    = 1

 9、非整数型的枚举的示例（元组类型传入实例化）

import enum


class BugStatus(enum.Enum):
    new = (7, ['incomplete',
               'invalid',
               'wont_fix',
               'in_progress'])
    incomplete = (6, ['new', 'wont_fix'])
    invalid = (5, ['new'])
    wont_fix = (4, ['new'])
    in_progress = (3, ['new', 'fix_committed'])
    fix_committed = (2, ['in_progress', 'fix_released'])
    fix_released = (1, ['new'])

    def __init__(self, num, transitions):
        self.num = num
        self.transitions = transitions

    def can_transition(self, new_state):
        return new_state.name in self.transitions


print('Name:', BugStatus.in_progress)
print('Value:', BugStatus.in_progress.value)
print('Custom attribute:', BugStatus.in_progress.transitions)
print('Using attribute:',
      BugStatus.in_progress.can_transition(BugStatus.new))

运行效果

Name: BugStatus.in_progress
Value: (3, ['new', 'fix_committed'])
Custom attribute: ['new', 'fix_committed']
Using attribute: True

10、非整数型的枚举的示例（字典+元组类型传入实例化）

 运行效果

Name: BugStatus.in_progress
Value: {'num': 3, 'transitions': ['new', 'fix_committed']}
Custom attribute: ['new', 'fix_committed']
Using attribute: True