Enumerate variables with Enum!

Enum is a way that Python enumerate variables. The enum module allows for the creation of enumerated constants—unique, immutable data types that are useful for representing a fixed set of values. These values, which are usually related by their context, are known as enumeration members.

Enum provides…

1. Uniqueness - Each member of an Enum is unique within its definition, meaning no two members can have the same value. Attempting to define two members with the same value will result in an error unless you explicitly allow aliases.
2. Immutability - Enum members are immutable. Once the Enum class is defined, you cannot change the members or their values.
3. Iterability and Comparability - Enum classes support iteration over their members and can be compared using identity and equality checks.
4. Accessing Members - You can access enumeration members by their names or values:
5. Auto - If you want to automatically assign values to enum members, you can use the auto() function from the same module:

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from enum import Enum

class State(Enum):
	PLAYING=0
	PAUSED=1
	GAME_OVER=2

If we just want to make sure them to be unique and automatically assigned, then use auto()

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from enum import Enum, auto

class State(Enum):
	PLAYING=auto()
	PAUSED=auto()
	GAME_OVER=auto()

print(State.PLAYING)
print(State.PLAYING.value)

Or simply,

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from enum import Enum, auto

class State(Enum):
	PLAYING, PAUSED, GAME_OVER=range(3)

print(State.PLAYING)
print(State.PLAYING.value)

• However, this hard codes numbers, which can create an issue in the future.

Iterating over Enum Members

You can iterate over the members of an enum:

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for state in State:
    print(state)

Comparison of Enum Members

Enum members are singleton objects, so comparison is possible by identity:

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if State.PLAYING is State.PLAYING:
    print("RED is indeed RED")

Using Enum as a Type Hint

Enums can be used as type hints, enhancing code readability and correctness:

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def paint(color: Color):
    print(f"Painting with {color.name}")

Extending Enums: IntEnum and StrEnum

For enums where the members are specifically integers or strings, you can inherit from IntEnum or StrEnum for additional benefits, like being able to compare members to integers or strings directly.

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from enum import IntEnum

class Priority(IntEnum):
    LOW = 1
    MEDIUM = 2
    HIGH = 3

# Direct comparison with integers
if Priority.LOW < Priority.HIGH:
    print("Low priority is less than high")

Unique Constraint

To ensure that all enum values are unique, you can use the @unique decorator:

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from enum import Enum, unique

@unique
class StatusCode(Enum):
    OK = 200
    NOT_FOUND = 404
    ERROR = 500

Using @unique will raise a ValueError if any duplicate values are detected.

Conclusion

Enums in Python are useful for defining sets of named constants that are related and have a fixed set of members. They improve code readability, prevent errors related to using incorrect literal values, and can simplify type checking and validation in your programs.