面向对象高级编程 Enum(枚举)、@unique

最新推荐文章于 2022-09-05 17:00:25 发布

一颗苹果i

最新推荐文章于 2022-09-05 17:00:25 发布

阅读量2.4k

点赞数 3

CC 4.0 BY-SA版权

分类专栏： python 文章标签： python

本文链接：https://blog.youkuaiyun.com/qq_38936266/article/details/97944679

python 专栏收录该内容

7 篇文章

订阅专栏

本文介绍了Python中的Enum枚举类，展示了当枚举类中存在重复值时的处理方式，并探讨了@unique装饰器在防止枚举值重复上的作用。同时，讨论了如何通过__members__属性来查看枚举成员。最后，提到了枚举成员的比较特性，强调它们不能直接比较大小，但可以比较值是否相等。

seasons = ['Spring', 'Summer', 'Fall', 'Winter']
print (list(enumerate(seasons)))

运行结果：

[(0, 'Spring'), (1, 'Summer'), (2, 'Fall'), (3, 'Winter')]

from enum import Enum

Month = Enum('month', ('Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'))

for name, member in Month.__members__.items():
    print(name, '=>', member, ',', member.value)

运行结果：

Jan => month.Jan , 1
Feb => month.Feb , 2
Mar => month.Mar , 3
Apr => month.Apr , 4
May => month.May , 5
Jun => month.Jun , 6
Jul => month.Jul , 7
Aug => month.Aug , 8
Sep => month.Sep , 9
Oct => month.Oct , 10
Nov => month.Nov , 11
Dec => month.Dec , 12

当Class中有重复值时，会返回第一个，其他忽略

from enum import Enum

class Weekday(Enum):
monday = 1
tusday = 1
wensdday =3
thursday =9
friday =5
#print (Weekday(1))

for n in Weekday:
print (n)

运行结果：

Weekday.monday
Weekday.wensdday
Weekday.thursday
Weekday.friday

手动打Enum值时，一不小心打错了怎么办，又得一个个找，真麻烦。所以，有人想，如果有个方法能够检查重复值就好了，于是：@unique就出来了

from enum import Enum, 
@unique
class Weekday(Enum):
    monday = 1
    tusday = 1
    wensdday =3
    thursday =9
    friday =5
print (Weekday(1))

运行结果：

Traceback (most recent call last):
  File "/usercode/file.py", line 7, in <module>
    class Weekday(Enum):
  File "/usr/lib/python3.4/enum.py", line 524, in unique
    (enumeration, alias_details))
  ValueError: duplicate values found in <enum 'Weekday'>: tusday -> monday

4.有人也在想，我就是不改咋地！我能不能通过另一个方法把成员都打印出来？于是：__members__就出来了

from enum import Enum

class Weekday(Enum):
    monday = 1
    tusday = 1
    wensdday = 3
    thursday = 9
    friday = 5

for n,y in Weekday.__members__.items():
    print (n, '--', y, '--',  y.value)
    
f = Weekday.thursday
print (f.value)

运行结果：

monday – Weekday.monday – 1
tusday – Weekday.tusday – 1
wensdday – Weekday.wensdday – 3
thursday – Weekday.thursday – 9
friday – Weekday.friday – 5

9
5.枚举比较：不能比大小！！能比同值

from enum import Enum, unique

#@unique
class Weekday(Enum):
    monday = 1
    tusday = 1
    wensdday =3
    thursday =9
    friday =5

print (Weekday.monday == Weekday.wensdday)
print (Weekday.tusday is Weekday.friday )

print (Weekday.tusday > Weekday.friday )

运行结果：

False
False

Traceback (most recent call last):
  File "/usercode/file.py", line 16, in <module>
    print (Weekday.tusday > Weekday.friday )
TypeError: unorderable types: Weekday() > Weekday()

非原创，文章内容来自网络