python工具庫介紹-enum: 列舉

摘要： 簡介 列舉是常量的集合，支援根據id比較和迭代等功能。 建立列舉 繼承Enum類，新增類屬性即可建立列舉。 enum_create.py #!python #!/usr/bin/env python # -*- coding: utf-8 -*- ...

簡介

列舉是常量的集合，支援根據id比較和迭代等功能。

建立列舉

繼承Enum類，新增類屬性即可建立列舉。

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))

執行結果

#!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()

可見每個列舉成員都有name和value，順序和建立順序一致，但不用它們進行排序，列舉成員之間不能進行比較。

IntEnum類可以基於value進行比較：

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)))

執行結果：

#!python

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

唯一性

預設後面出現的重複值為別名:

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)

執行結果

#!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

通過裝飾符@enum.unique可以保證唯一性

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

執行結果

#!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

構造方法建立列舉

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))

執行結果：

#!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

建構函式自動生成的value從0開始。還可以從元組或者字典構成的列表等生成。

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))

執行結果

#!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', ],
}## 簡介

列舉是常量的集合，支援根據id比較和迭代等功能。

參考資料：
----------------------------------------------

* python中文庫參考專案：https://bitbucket.org/china-testing/python-chinese-library

* python中文庫參考專案文件：https://bitbucket.org/china-testing/python-chinese-library/wiki/browse/

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* 相關文件下載地址：https://bitbucket.org/china-testing/python-chinese-library/downloads

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

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

* 完稿日期：2016.08.22

## 建立列舉

繼承Enum類，新增類屬性即可建立列舉。

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))

執行結果

!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()

可見每個列舉成員都有name和value，順序和建立順序一致，但不用它們進行排序，列舉成員之間不能進行比較。

IntEnum類可以基於value進行比較：

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)))

執行結果：

!python

$ python3 enum_intenum.py

Ordered by value:

fix_released

fix_committed

in_progress

wont_fix

invalid

incomplete

new

## 唯一性

預設後面出現的重複值為別名:

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)

執行結果

!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

通過裝飾符@enum.unique可以保證唯一性

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

執行結果

!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

## 構造方法建立列舉

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))

執行結果：

!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

建構函式自動生成的value從0開始。還可以從元組或者字典構成的列表等生成。

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))

執行結果

!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))

執行結果

!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))

執行結果

#!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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