简介

枚举是常量的集合，支持根据id比较和迭代等功能。

创建枚举

继承Enum类，添加类属性即可创建枚举。

enum_create.py

#!python

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Author Rongzhong Xu 2016-08-22 wechat: pythontesting
"""
Name: enum_create.py
Tesed in python3.5

The members are produced in the order they are declared in the class
definition. The names and values are not used to sort them in any way.
"""
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))
print()

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


# Comparing Enums
# Because enumeration members are not ordered,
# they only support comparison by identity and equality.
actual_state = BugStatus.wont_fix
desired_state = BugStatus.fix_released

print('Equal   :',
      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))

执行结果

#!python

$ python3 enum_create.py 

Member name: wont_fix
Member value: 4

new             = 7
incomplete      = 6
invalid         = 5
wont_fix        = 4
in_progress     = 3
fix_committed   = 2
fix_released    = 1
Equal   : False True
Identity: False True
Ordered by value:
  Cannot sort: unorderable types: BugStatus() < BugStatus()

可见每个枚举成员都有name和value，顺序和创建顺序一致，但不用它们进行排序，枚举成员之间不能进行比较。

IntEnum类可以基于value进行比较：

enum_intenum.py

#!python

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)))

执行结果：

#!python

$ python3 enum_intenum.py
Ordered by value:
  fix_released
  fix_committed
  in_progress
  wont_fix
  invalid
  incomplete
  new

唯一性

默认后面出现的重复值为别名:

enum_aliases.py

#!python
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)

执行结果

#!python

$ python3 enum_aliases.py 
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

通过装饰符@enum.unique可以保证唯一性

enum_unique_enforce.py

#!python

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

    # This will trigger an error with unique applied.
    by_design = 4
    closed = 1

执行结果

#!python

$ python3 enum_unique_enforce.py 
Traceback (most recent call last):
  File "enum_unique_enforce.py", line 16, in <module>
    class BugStatus(enum.Enum):
  File "/usr/lib/python3.5/enum.py", line 573, in unique
    (enumeration, alias_details))
ValueError: duplicate values found in <enum 'BugStatus'>: by_design -> wont_fix, closed -> fix_released

构造方法创建枚举

enum_programmatic_create.py

#!python

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))

执行结果：

#!python

$ python3 enum_programmatic_create.py

Member: BugStatus.new

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

构造函数自动生成的value从0开始。还可以从元组或者字典构成的列表等生成。

enum_programmatic_mapping.py

#!python

import enum


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

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

执行结果

#!python

 python3 enum_programmatic_mapping.py
All members:
new             = 7
incomplete      = 6
invalid         = 5
wont_fix        = 4
in_progress     = 3
fix_committed   = 2
fix_released    = 1

非整型的value

enum_complex_values.py

#!python

import enum


class BugStatus(enum.Enum):

    new = {
        'value': 7,
        'transitions': ['incomplete', 'invalid', 'wont_fix', 'in_progress', ],
    }## 简介

枚举是常量的集合，支持根据id比较和迭代等功能。

参考资料：
----------------------------------------------

* python中文库参考项目：  https://bitbucket.org/china-testing/python-chinese-library

* python中文库参考项目文档：https://bitbucket.org/china-testing/python-chinese-library/wiki/browse/

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* 相关文档下载地址：https://bitbucket.org/china-testing/python-chinese-library/downloads

* python官方文档：https://docs.python.org/3/library/enum.html

* pymotw文档：https://pymotw.com/3/enum/index.html

* 完稿日期：2016.08.22

## 创建枚举

继承Enum类，添加类属性即可创建枚举。

enum_create.py

!python

!/usr/bin/env python

-- coding: utf-8 --

Author Rongzhong Xu 2016-08-22 wechat: pythontesting

"""
Name: enum_create.py
Tesed in python3.5

The members are produced in the order they are declared in the class
definition. The names and values are not used to sort them in any way.
"""
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))
print()

Iteration

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

Comparing Enums

Because enumeration members are not ordered,

they only support comparison by identity and equality.

actual_state = BugStatus.wont_fix
desired_state = BugStatus.fix_released

print('Equal :',
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))

执行结果

!python

$ python3 enum_create.py

Member name: wont_fix
Member value: 4

new = 7
incomplete = 6
invalid = 5
wont_fix = 4
in_progress = 3
fix_committed = 2
fix_released = 1
Equal : False True
Identity: False True
Ordered by value:
Cannot sort: unorderable types: BugStatus() < BugStatus()

可见每个枚举成员都有name和value，顺序和创建顺序一致，但不用它们进行排序，枚举成员之间不能进行比较。

IntEnum类可以基于value进行比较：

enum_intenum.py

!python

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)))

执行结果：

!python

$ python3 enum_intenum.py
Ordered by value:
fix_released
fix_committed
in_progress
wont_fix
invalid
incomplete
new

## 唯一性

默认后面出现的重复值为别名:

enum_aliases.py

!python

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)

执行结果

!python

$ python3 enum_aliases.py
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

通过装饰符@enum.unique可以保证唯一性

enum_unique_enforce.py

!python

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

# This will trigger an error with unique applied.
by_design = 4
closed = 1

执行结果

!python

$ python3 enum_unique_enforce.py
Traceback (most recent call last):
File "enum_unique_enforce.py", line 16, in <module>
class BugStatus(enum.Enum):
File "/usr/lib/python3.5/enum.py", line 573, in unique
(enumeration, alias_details))
ValueError: duplicate values found in <enum 'BugStatus'>: by_design -> wont_fix, closed -> fix_released

## 构造方法创建枚举

enum_programmatic_create.py

!python

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))

执行结果：

!python

$ python3 enum_programmatic_create.py

Member: BugStatus.new

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

构造函数自动生成的value从0开始。还可以从元组或者字典构成的列表等生成。

enum_programmatic_mapping.py

!python

import enum

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

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

执行结果

!python

python3 enum_programmatic_mapping.py
All members:
new = 7
incomplete = 6
invalid = 5
wont_fix = 4
in_progress = 3
fix_committed = 2
fix_released = 1

## 非整型的value

enum_complex_values.py

!python

import enum

class BugStatus(enum.Enum):

new = {
    'value': 7,
    'transitions': ['incomplete', 'invalid', 'wont_fix', 'in_progress', ],
}
incomplete = {
    'value': 6,
    'transitions': ['new', 'wont_fix'],
}
invalid = {
    'value': 5,
    'transitions': ['new'],
}
wont_fix = {
    'value': 4,
    'transitions': ['new'],
}
in_progress = {
    'value': 3,
    'transitions': ['new', 'fix_committed'],
}
fix_committed = {
    'value': 2,
    'transitions': ['in_progress', 'fix_released'],
}
fix_released = {
    'value': 1,
    'transitions': ['new'],
}

def __init__(self, vals):
    self.num = vals['value']
    self.transitions = vals['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))

执行结果

!python

python3 enum_complex_values.py
Name: BugStatus.in_progress
Value: {'transitions': ['new', 'fix_committed'], 'value': 3}
Custom attribute: ['new', 'fix_committed']
Using attribute: True

    incomplete = {
        'value': 6,
        'transitions': ['new', 'wont_fix'],
    }
    invalid = {
        'value': 5,
        'transitions': ['new'],
    }
    wont_fix = {
        'value': 4,
        'transitions': ['new'],
    }
    in_progress = {
        'value': 3,
        'transitions': ['new', 'fix_committed'],
    }
    fix_committed = {
        'value': 2,
        'transitions': ['in_progress', 'fix_released'],
    }
    fix_released = {
        'value': 1,
        'transitions': ['new'],
    }

    def __init__(self, vals):
        self.num = vals['value']
        self.transitions = vals['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))

执行结果

#!python

 python3 enum_complex_values.py
Name: BugStatus.in_progress
Value: {'transitions': ['new', 'fix_committed'], 'value': 3}
Custom attribute: ['new', 'fix_committed']
Using attribute: True

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