一文带你了解Python枚举类enum的使用
作者：XerCis
枚举是与多个唯一常量绑定的一组符号，因为枚举表示的是常量，建议枚举成员名用大写 IntEnum 便于进行系统交互。本文将通过一些示例代码讲解Python枚举类的使用，需要的可以参考一下
简介
枚举是与多个唯一常量绑定的一组符号
因为枚举表示的是常量，建议枚举成员名用大写
IntEnum 便于进行系统交互
初试
from enum import Enum
class Color(Enum):
RED = 1
GREEN = 2
BLUE = 3
print(Color.RED) # Color.RED
print(repr(Color.RED)) # <Color.RED: 1>
print(type(Color.RED)) # <enum 'Color'>
print(isinstance(Color.GREEN, Color)) # True
print(Color.RED.name) # RED
遍历
from enum import Enum
class Shake(Enum):
VANILLA = 7
CHOCOLATE = 4
COOKIES = 9
MINT = 3
for shake in Shake:
print(shake)
# Shake.VANILLA
# Shake.CHOCOLATE
# Shake.COOKIES
# Shake.MINT
__members__ 列出 name 和成员
from enum import Enum
class Shape(Enum):
SQUARE = 2
DIAMOND = 1
CIRCLE = 3
ALIAS_FOR_SQUARE = 2
for name, member in Shape.__members__.items():
print(name, member)
# SQUARE Shape.SQUARE
# DIAMOND Shape.DIAMOND
# CIRCLE Shape.CIRCLE
# ALIAS_FOR_SQUARE Shape.SQUARE
可哈希
枚举成员可哈希，可用于字典和集合
from enum import Enum
class Color(Enum):
RED = 1
GREEN = 2
BLUE = 3
apples = {}
apples[Color.RED] = 'red delicious'
apples[Color.GREEN] = 'granny smith'
print(apples)
# {<Color.RED: 1>: 'red delicious', <Color.GREEN: 2>: 'granny smith'}
访问成员
- name：变量名
- value：值
from enum import Enum
class Color(Enum):
RED = 1
GREEN = 2
BLUE = 3
# 通过值访问
print(Color(1)) # Color.RED
print(Color(3)) # Color.BLUE
# 通过name访问
print(Color['RED']) # Color.RED
print(Color['GREEN']) # Color.GREEN
# 访问成员的name或value
print(Color.RED.name) # RED
print(Color.RED.value) # 1
唯一枚举值
装饰器 @unique
from enum import Enum, unique
@unique
class Mistake(Enum):
ONE = 1
TWO = 2
THREE = 3
FOUR = 3
# ValueError: duplicate values found in <enum 'Mistake'>: FOUR -> THREE
自动枚举值
如果枚举值不重要，可以用 auto()， 默认从 1 开始
from enum import Enum, auto
class Color(Enum):
RED = auto()
BLUE = auto()
GREEN = auto()
print(Color(1)) # Color.RED
print(list(Color)) # [<Color.RED: 1>, <Color.BLUE: 2>, <Color.GREEN: 3>]
比较运算
- Enum 不支持直接排序
- IntEnum 可直接排序
Enum
from enum import Enum
class Color(Enum):
RED = 1
BLUE = 2
GREEN = 3
print(Color.RED is Color.RED) # True
print(Color.RED is Color.BLUE) # False
print(Color.RED is not Color.BLUE) # True
try:
Color.RED < Color.BLUE # Enum不支持直接排序
except Exception as e:
print(e) # '<' not supported between instances of 'Color' and 'Color'
print(Color.BLUE == Color.RED) # Fasle
print(Color.BLUE != Color.RED) # True
print(Color.BLUE == Color.BLUE) # True
print(Color.BLUE == 2) # False
IntEnum
from enum import IntEnum
class Color(IntEnum):
RED = 1
BLUE = 2
GREEN = 3
# IntEnum可直接排序
print(Color.RED < Color.BLUE) # True
print(Color.BLUE == 2) # True
功能性API
from enum import Enum
class Animal(Enum):
ANT = 1
BEE = 2
CAT = 3
DOG = 4
Animal = Enum('Animal', 'ANT BEE CAT DOG') # 同上
print(Animal) # <enum 'Animal'>
print(Animal.ANT) # <Animal.ANT: 1>
print(Animal.ANT.value) # 1
print(list(Animal)) # [<Animal.ANT: 1>, <Animal.BEE: 2>, <Animal.CAT: 3>, <Animal.DOG: 4>]
IntEnum
除了不可以直接和 Enum 比较，其他都类似整数
from enum import Enum, IntEnum
class Color(Enum):
RED = 1
GREEN = 2
class Shape(IntEnum):
CIRCLE = 1
SQUARE = 2
class Request(IntEnum):
POST = 1
GET = 2
print(Shape.CIRCLE == Color.RED) # False
print(Shape == 1) # False
print(Shape.CIRCLE == 1) # True
print(Shape.CIRCLE == Request.POST) # True
print(int(Shape.CIRCLE)) # 1
print(['a', 'b', 'c'][Shape.CIRCLE]) # b
print([i for i in range(Shape.SQUARE)]) # [0, 1]
IntFlag
类似 int，IntFlag 成员使用按位运算符得到的结果仍然是 IntFlag 成员
IntFlag 和 Enum 的一个区别在于，如果没有设置任何标志（值为 0），则其布尔值为 False
from enum import IntFlag
class Perm(IntFlag):
R = 4 # 读
W = 2 # 写
X = 1 # 执行
print(Perm.R | Perm.W) # <Perm.R|W: 6>
print(Perm.R + Perm.W) # 6
RW = Perm.R | Perm.W
print(Perm.R in RW) # True
from enum import IntFlag
class Perm(IntFlag):
R = 4 # 读
W = 2 # 写
X = 1 # 执行
RWX = 7 # 读写执行
print(Perm.RWX) # <Perm.RWX: 7>
print(~Perm.RWX) # <Perm.-8: -8>
print(Perm.R & Perm.X) # <Perm.0: 0>
print(bool(Perm.R & Perm.X)) # False
print(Perm.X | 8) # <Perm.8|X: 9>
Flag
- Flag 与 IntFlag 类似，成员可使用按位运算符进行组合，但不可与其他 Flag 或 int 组合
- 推荐用 auto() 作为值
from enum import Flag, auto
class Color(Flag):
BLACK = 0
RED = auto()
BLUE = auto()
GREEN = auto()
WHITE = RED | BLUE | GREEN
print(Color.RED & Color.GREEN) # <Color.0: 0>
print(bool(Color.RED & Color.GREEN)) # False
print(Color.WHITE) # <Color.WHITE: 7>
print(Color.BLACK) # <Color.BLACK: 0>
print(bool(Color.BLACK)) # False
知识点
不支持同名
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