Enums

Python · Reference cheat sheet

📋 Overview

enum.Enum defines a set of named symbolic values. Use enums instead of magic strings/ints for status codes, modes, and options. Python 3.11+ adds StrEnum, improved Flag, and more.

🔧 Core concepts

Type	Use
`Enum`	Classic named values
`IntEnum`	Comparable to `int`
`StrEnum`	`str` mixin (3.11+)
`Flag` / `IntFlag`	Bitwise combinations
`auto()`	Auto-assign values
`enum.unique`	Decorator: forbid duplicate values

Members are singletons: Color.RED is Color.RED. Access by name (Color["RED"]) or value (Color(1)).

💡 Examples

Basic Enum:

from enum import Enum, auto

class Status(Enum):
    PENDING = auto()
    RUNNING = auto()
    DONE = auto()

s = Status.RUNNING
print(s.name, s.value)
print(Status["DONE"])

StrEnum (3.11+):

from enum import StrEnum

class Role(StrEnum):
    ADMIN = "admin"
    USER = "user"

def greet(role: Role) -> str:
    return f"hello {role}"  # role is a str

assert Role.ADMIN == "admin"

Flags:

from enum import Flag, auto

class Perm(Flag):
    READ = auto()
    WRITE = auto()
    EXEC = auto()

rw = Perm.READ | Perm.WRITE
print(Perm.READ in rw)
print(bool(rw & Perm.EXEC))

Match (3.10+):

match Status.DONE:
    case Status.PENDING | Status.RUNNING:
        print("busy")
    case Status.DONE:
        print("finished")
    case _:
        print("unknown")

⚠️ Pitfalls

Comparing Enum to raw ints fails unless you use IntEnum.
Functional API Enum("Color", "RED GREEN") is less readable for large enums.
Pickling / JSON: serialize .value or .name explicitly.
Do not mutate .value on members.
auto() values depend on declaration order — stable only if you don't reorder carelessly.

Enums

Enums

📋 Overview

🔧 Core concepts

💡 Examples

⚠️ Pitfalls

🔗 Related

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