Enums in Python

Enums in Python : Enumerate Your Values

Enums are a way to create a set of symbolic names (members) bound to unique, constant values. They are a way to define a set of named constants. Enums are defined using the enum module. Enumerations are created using classes. Enums have names and values associated with them. Enums are defined by creating a new class that inherits from Enum. Enums can be iterated over. Enums can be compared using == and is.

Syntax

The syntax for creating an Enum in Python is as follows:

Enum Syntax

from enum import Enum
 
class EnumName(Enum):
    MEMBER1 = value1
    MEMBER2 = value2
    MEMBER3 = value3
    ...

In the above syntax:

• EnumName is the name of the Enum.
• MEMBER1, MEMBER2, MEMBER3, etc. are the members of the Enum.
• value1, value2, value3, etc. are the values associated with the members.

Creating Enums

To create an Enum, you need to import the Enum class from the enum module. Then, you can create a new class that inherits from Enum. Each member of the Enum is defined as a class attribute. The value of the member is passed as an argument to the Enum constructor. The value of the member can be any type, such as an integer, string, or float.

Enums in Python

from enum import Enum
 
class Color(Enum):
    RED = 1
    GREEN = 2
    BLUE = 3

In the above code:

• Color is the name of the Enum.
• RED, GREEN, and BLUE are the members of the Enum.
• 1, 2, and 3 are the values associated with the members.
• The members of the Enum are accessed using the dot notation, e.g., Color.RED, Color.GREEN, Color.BLUE.
• The members of the Enum can be compared using == and is.

Iterating Over Enums

Enums can be iterated over using a for loop. When you iterate over an Enum, you get the members of the Enum.

Iterating Over Enums

from enum import Enum
 
class Color(Enum):
    RED = 1
    GREEN = 2
    BLUE = 3
 
for color in Color:
    print(color)

In the above code, the output will be:

Output

C:/Users/username/desktop>python enum.py
Color.RED
Color.GREEN
Color.BLUE

Comparing Enums

Enums can be compared using the == and is operators. When you compare two Enums using the == operator, it compares the values of the Enums. When you compare two Enums using the is operator, it compares the memory addresses of the Enums.

Comparing Enums

from enum import Enum
 
class Color(Enum):
    RED = 1
    GREEN = 2
    BLUE = 3
 
color1 = Color.RED
color2 = Color.RED
 
print(color1 == color2) # Output: True
print(color1 is color2) # Output: True

In the above code, the output will be:

Output

C:/Users/username/desktop>python enum.py
True
True

Enum Members

You can access the members of an Enum using the dot notation. The members of an Enum are instances of the Enum class.

Accessing Enum Members

from enum import Enum
 
class Color(Enum):
    RED = 1
    GREEN = 2
    BLUE = 3
 
print(Color.RED) 
print(Color.GREEN)
print(Color.BLUE)

In the above code, the output will be:

Output

C:/Users/username/desktop>python enum.py
Color.RED
Color.GREEN
Color.BLUE

Danger

Enums are not hashable, so they cannot be used as keys in dictionaries. you can’t assign same value to different members of Enum.

Enums are not hashable

from enum import Enum
 
class Color(Enum):
    RED = 1
    GREEN = 1
    BLUE = 3

The above code will raise a ValueError as GREEN and RED have the same value.

Output

C:/Users/username/desktop>python enum.py
Traceback (most recent call last):
  File "enum.py", line 5, in <module>
    class Color(Enum):
  File "C:\Users\username\AppData\Local\Programs\Python\Python39\lib\enum.py", line 225, in __new__
    raise ValueError("%r is a duplicate of %r" % (alias, name))
ValueError: duplicate values found in <enum 'Color'>: GREEN -> RED

Tip

Alternatively, you can use different syntax to create Enum members with the same value.

Enums with same value

from enum import Enum
 
colors = Enum('colors', 'RED GREEN BLUE')
 
print(colors.RED)
print(colors.GREEN)
print(colors.BLUE)

The above code will output:

Output

C:/Users/username/desktop>python enum.py
colors.RED
colors.GREEN
colors.BLUE

Accessing Enum Members

You can access the members of an Enum using the dot notation. The members of an Enum are instances of the Enum class.

Accessing Enum Members

from enum import Enum
 
class Color(Enum):
    RED = 1
    GREEN = 2
    BLUE = 3
 
currentColor = Color.RED
print(type(currentColor))
print(currentColor.name)
print(currentColor.value)

In the above code, the output will be:

Output

C:/Users/username/desktop>python enum.py
<enum 'Color'>
RED
1

In the above code:

• currentColor is an instance of the Color Enum.
• currentColor.name returns the name of the Enum member.
• currentColor.value returns the value of the Enum member.

Accessing Enum Members using Iteration

You can access the members of an Enum using iteration. When you iterate over an Enum, you get the members of the Enum.

Accessing Enum Members using Iteration

from enum import Enum
 
class Color(Enum):
    RED = 1
    GREEN = 2
    BLUE = 3
 
for color in Color:
    print(color.name, color.value)

In the above code, the output will be:

Output

C:/Users/username/desktop>python enum.py
RED 1
GREEN 2
BLUE 3

A Real-World Example

Here is a real-world example of using Enums in Python. In this example, we define an Enum called Weekday that represents the days of the week. We then create a function that takes a Weekday Enum as an argument and prints the name of the day.

Real-World Example

from enum import Enum
 
class Weekday(Enum):
    MONDAY = 1
    TUESDAY = 2
    WEDNESDAY = 3
    THURSDAY = 4
    FRIDAY = 5
    SATURDAY = 6
    SUNDAY = 7
 
def print_day(day):
    print(day.name)
 
print_day(Weekday.MONDAY)
print_day(Weekday.FRIDAY)

In the above code, the output will be:

Output

C:/Users/username/desktop>python enum.py
MONDAY
FRIDAY

sketch Enum members, aliases, and what equals what p5.js Pause Restart

Two things surprise people. A second name with the same value is not a new member -- it is an ALIAS, so it is missing from iteration and is the identical object as the original. And a plain Enum member does not compare equal to its own value: Color.RED == 1 is False, because the whole point is a distinct type. If you want it to equal the integer, that is what IntEnum is for. Every line here was run.

Conclusion

In this tutorial, you learned about Enums in Python. Enums are a way to create a set of symbolic names (members) bound to unique, constant values. Enums are defined using the enum module. Enums are created using classes. Enums have names and values associated with them. Enums can be iterated over. Enums can be compared using == and is. For more information on Enums, you can refer to the official documentation. For more tutorials on Python Central Hub.

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Try it: Enum Exercises

Exercise 1 – Basic Enum

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Exercise 2 – Iterating Enum

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Exercise 3 – Enum Comparison

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