ValueError: Invalid Enum Value

Why This Happens

Enums have a fixed set of valid values. Calling Color('invalid') raises ValueError. This often happens when deserializing data from external sources.

The Problem

from enum import Enum

class Color(Enum):
    RED = 'red'
    GREEN = 'green'

color = Color('yellow')

The Fix

from enum import Enum

class Color(Enum):
    RED = 'red'
    GREEN = 'green'

try:
    color = Color(user_input)
except ValueError:
    color = Color.RED

Step-by-Step Fix

1. 1

   Handle invalid values

   Wrap in try/except ValueError.

2. 2

   List valid values

   Use [e.value for e in Enum] in error messages.

3. 3

   Use a default

   Provide a sensible default for invalid input.