Python Enum Declaration

In Python, an Enum (short for Enumeration) is a data type that contains a set of named values. It is used to define a group of constants that are readily identifiable by their names.

Declaring an Enum

To create an Enum in Python, we use the enum module. Here is an example of declaring an Enum:

from enum import Enum

class Fruit(Enum):
    APPLE = 1
    BANANA = 2
    ORANGE = 3

In this example, we define an Enum called Fruit. The constants within the Enum are defined using class attributes. Each constant is given a name, followed by its value.

Using Enum Constants

Once an Enum is defined, we can use its constants in our code. Here is an example:

favorite_fruit = Fruit.APPLE
print(f"My favorite fruit is {favorite_fruit.name}.")

In this example, we create a variable favorite_fruit and set it to the value Fruit.APPLE. We then use the name attribute to retrieve the name of the constant.

Enum Methods

The enum module provides several methods that can be used with Enum constants. Here are some examples:

Accessing Enum Constants by Value

fruit_value = 2
fruit = Fruit(fruit_value)
print(fruit.name)

In this example, we create a variable fruit_value and set it to the value of 2. We then use the Fruit constructor to create an Enum constant with the value of 2, and assign it to the variable fruit. We then print the name of the constant.

Iterating Over Enum Constants

for fruit in Fruit:
    print(fruit.name)

In this example, we use a for loop to iterate over all of the constants in the Fruit Enum. We then print the name of each constant.

Accessing Enum Constants by Name

fruit_name = "APPLE"
fruit = Fruit[fruit_name]
print(fruit.value)

In this example, we create a variable fruit_name and set it to "APPLE". We then use the bracket notation to access the APPLE constant from the Fruit Enum, and assign it to the variable fruit. We then print the value of the constant.

Conclusion

Declaring an Enum in Python is a simple and effective way to group together related constants. Once an Enum is defined, its constants can be used in our code, and several methods are available to work with Enum constants.