When we need to define constants, one way is to use uppercase variables to define integers, such as months

JAN = 1
FEB = 2
MAR = 3
APR=4
May=5
Jun=6
Jul=7
Aug=8
Sep=9
Oct=10
NOV = 11
DEC = 12

The advantage is simplicity, the disadvantage is the type int, and it is still a variable.

A better way is to define a class type for such an enumeration type, and then each constant is a unique instance of class. Python provides the Enum class to implement this function:

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

In this way, we get the enumeration class of Month type. You can directly use Month.Jan to reference a constant or enumerate all its members.

>>> Month.Jan
<Month.Jan: 1>
>>> Month.Feb
<Month.Feb: 2>

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

The value attribute is an int constant automatically assigned to a member, counting from 1 by default

If you need more precise control over enumeration types, you can derive custom classes from Enum

from enum import Enum,unique
@unique
class Weekday(Enum):
    Sun=0
    Mon=1
    Tue=2
    Wed=3
    Thu=4
    Fri=5
    Sat=6

Decorator unique ensures no repetition

There are several ways to access these enumeration values

>>> day1 = Weekday.Mon
>>> print(day1)
Weekday.Mon
>>> print(Weekday.Tue)
Weekday.Tue
>>> print(Weekday['Tue'])
Weekday.Tue
>>> print(Weekday.Tue.value)
2
>>> print(day1 == Weekday.Mon)
True
>>> print(day1 == Weekday.Tue)
False
>>> print(Weekday(1))
Weekday.Mon
>>> print(day1 == Weekday(1))
True
>>> Weekday(7)
Traceback (most recent call last):
  ...
ValueError: 7 is not a valid Weekday
>>> for name, member in Weekday.__members__.items():
...     print(name, '=>', member)
...
Sun => Weekday.Sun
Mon => Weekday.Mon
Tue => Weekday.Tue
Wed => Weekday.Wed
Thu => Weekday.Thu
Fri => Weekday.Fri
Sat => Weekday.Sat

It can be seen that enumeration constants can be referenced with member names and obtained directly from the value.

Practice

Changing Student's gender property to enumeration type can avoid using strings

from enum import Enum, unique
class Gender(Enum):
  Male=0
  Female=1
class Student(object):
    def __init__(self, name, gender):
        self.name = name
        self.gender = gender

bart=Student('Bart',Gender.Male)