Enum Basics

Enums represent a fixed set of values, providing type safety and code clarity. They're useful for representing distinct states or choices.

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Creating Basic Enums

from enum import Enum

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

class Size(Enum):
    SMALL = "S"
    MEDIUM = "M"
    LARGE = "L"
    XLARGE = "XL"

# Access members
print(Color.RED)          # Color.RED
print(Color.RED.name)     # 'RED'
print(Color.RED.value)    # 1

print(Size.MEDIUM)        # Size.MEDIUM
print(Size.MEDIUM.value)  # 'M'

Enum Iteration

from enum import Enum

class Status(Enum):
    PENDING = "pending"
    RUNNING = "running"
    COMPLETED = "completed"
    FAILED = "failed"

# Iterate over all members
for status in Status:
    print(f"{status.name}: {status.value}")

# Get all values
values = [s.value for s in Status]
print(values)  # ['pending', 'running', 'completed', 'failed']

# Get all names
names = [s.name for s in Status]
print(names)   # ['PENDING', 'RUNNING', 'COMPLETED', 'FAILED']

Accessing Enum Members

from enum import Enum

class Priority(Enum):
    LOW = 1
    MEDIUM = 2
    HIGH = 3
    CRITICAL = 4

# By name
priority1 = Priority['HIGH']        # Priority.HIGH
priority2 = Priority.HIGH           # Priority.HIGH

# By value
priority3 = Priority(3)             # Priority.HIGH

# Comparison
print(Priority.HIGH == Priority.HIGH)      # True
print(Priority.HIGH == Priority.MEDIUM)    # False
print(Priority.HIGH.value == 3)            # True

Type Checking with Enums

from enum import Enum
from typing import Union

class Environment(Enum):
    DEVELOPMENT = "dev"
    STAGING = "staging"
    PRODUCTION = "prod"

def deploy(env: Environment):
    if env == Environment.PRODUCTION:
        print("⚠️ Deploying to PRODUCTION")
    elif env == Environment.STAGING:
        print("Deploying to staging")
    else:
        print("Deploying to development")

deploy(Environment.PRODUCTION)
# deploy("production")  # Type error - caught by linters

Enum Membership Testing

from enum import Enum

class HTTPMethod(Enum):
    GET = "GET"
    POST = "POST"
    PUT = "PUT"
    DELETE = "DELETE"
    PATCH = "PATCH"

def handle_request(method: str):
    try:
        http_method = HTTPMethod[method.upper()]
        print(f"Handling {http_method.value} request")
    except KeyError:
        print(f"Unknown HTTP method: {method}")

handle_request("GET")      # Works
handle_request("TRACE")    # Unknown HTTP method: TRACE

Enum Comparison and Ordering

from enum import Enum

class Grade(Enum):
    F = 1
    D = 2
    C = 3
    B = 4
    A = 5

grade1 = Grade.A
grade2 = Grade.C

print(grade1 == Grade.A)        # True
print(grade1 != grade2)         # True
# Can't use <, >, <=, >= on regular Enums

Best Practices

• Use Enums for fixed sets of values
• Provide descriptive names (not E1, E2, etc.)
• Keep enum definitions at module level
• Use type hints with Enum types
• Document what each member represents