python3 enum模块的应用实例详解
时间：2021-02-04 11:33:29|栏目：Python代码|点击： 次
一、枚举与字典类型
字典类型的缺点：
1.值可变
2.没有防止相同标签的功能
枚举的特点：
1.枚举类的值不可以被外界更改
2.不能存在相同的标签，但允许不同标签存在相同的枚举值，即后者相当于前者的别名
3.枚举值可以是任意类型
4.枚举标签尽量用大写
from enum import Enum #普通类
class dict():
green = 1
green = 2
red = 3
dict.red = 4
print(dict.red)
>>> 4
class VIP(Enum):
RED = 1
GREEN =2
YELLOW = 3
VIP.GREEN = 5 #枚举值不能动态更改
>>>File "D:\python\lib\enum.py", line 361, in __setattr__
raise AttributeError('Cannot reassign members.')
AttributeError: Cannot reassign members.
class VIP(Enum):
RED = 1
GREEN =2
YELLOW = 3
YELLOW = 3 #不能出现相同的标签
>>>File "D:\python\lib\enum.py", line 92, in __setitem__
raise TypeError('Attempted to reuse key: %r' % key)
TypeError: Attempted to reuse key: 'YELLOW'
class VIP(Enum):
RED = 1
GREEN =2
YELLOW = 3
BLUE = 3
print(VIP.BLUE)
>>>VIP.YELLOW #即VIP.BLUE类似于VIP.YELLOW的别名
class VIP(Enum):
RED = 1 #整型
BLUE = 1.2 #浮点型
GREEN = 'green' #str
YELLOW = True #布尔值
二、枚举类型、枚举名称、枚举值
1.获取枚举类型中的标签：.name属性
2.获取枚举类型中的值：.value属性
from enum import Enum
class VIP(Enum):
RED = 1
GREEN = 'green'
YELLOW = True
BLUE = 1.2
print(VIP.RED) #枚举的类型
print(VIP.YELLOW.name) #枚举的标签
print(VIP.YELLOW.value) #枚举的数值
print('遍历成员。。。')
for i in VIP.__members__.items(): #枚举的遍历
print(i)
>>>
VIP.RED
RED
1
遍历成员。。。
('RED', <VIP.RED: 1>)
('GREEN', <VIP.GREEN: 'green'>)
('YELLOW', <VIP.RED: 1>)
('BLUE', <VIP.BLUE: 1.2>)
三、枚举的比较运算
class VIP(Enum): RED = 1 GREEN = 'green' YELLOW = True BLUE = 2 #枚举的比较 a = VIP.RED == VIP.RED #枚举值可以做等值比较 b = VIP.RED == VIP.GREEN c = VIP.RED is VIP.RED d = VIP.RED == 1 #枚举标签与枚举值比较，并不相等 f = VIP.RED < VIP.BLUE #枚举值不支持大小比较，打印会报错TypeError: '<' not supported between instances of 'VIP' and 'VIP' print(a) print(b) print(c) print(d) >>> True False True False
四、枚举的转换
class VIP(Enum):
RED = 1
GREEN = 'green'
YELLOW = True
BLUE = 2
print(VIP(2)) #通过具体值获取枚举类型，返回VIP.BLUE
print(VIP('green')) #返回VIP.GREEN
五、枚举的拓展unique
unique:规定两个不同的枚举不能取相同的值
from enum import Enum,unique @unique class VIP(Enum): RED = 1 GREEN = 1 YELLOW = True BLUE = 2 >>>报错 ValueError: duplicate values found in <enum 'VIP'>: GREEN -> RED, YELLOW -> RED
六、枚举的拓展auto
如果我们对枚举值没有特别的要求或者没有太大的影响时，我们可以使用auto自动生成对应的数值
from enum import Enum,auto
class VIP(Enum):
RED = auto()
GREEN = auto()
YELLOW = auto()
BLUE = auto()
for i in VIP.__members__.items(): #遍历枚举
print(i)
>>>
('RED', <VIP.RED: 1>)
('GREEN', <VIP.GREEN: 2>)
('YELLOW', <VIP.YELLOW: 3>)
('BLUE', <VIP.BLUE: 4>)
其实，auto值是调用_generate_next_value_()函数来产生的，我们可以通过重写该函数
from enum import Enum,auto
class auto_test(Enum):
def _generate_next_value_(name, start, count, last_values):
return name
class VIP(auto_test):
RED = auto()
GREEN = auto()
YELLOW = auto()
BLUE = auto()
# for i in VIP.__members__.items(): #遍历枚举
# print(i)
print(list(VIP)) #转换列表
>>>
[<VIP.RED: 'RED'>, <VIP.GREEN: 'GREEN'>, <VIP.YELLOW: 'YELLOW'>, <VIP.BLUE: 'BLUE'>]
总结
