How to Create a Case-Insensitive Enum in Python

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Overview

Have you ever been tripped up by a simple typo? We’ve all been there. You write color = "Red", but somewhere else, your code checks for "red", and your program breaks. It’s an all-too-common bug when dealing with user input, API data, or configuration files.

The Python enum module is a fantastic tool for managing a fixed set of constants, but by default, it’s case-sensitive. This can cause frustrating errors if you aren’t careful. But what if there was a better way? What if your enum could handle "RED", "red", and "Red" all gracefully?

The solution is quite simple. Let’s do it.

How to create case insensitive enum

First, let’s create one enum class to handle the missing values:

class CaseInsensitiveEnum(Enum):
    @classmethod
    def _missing_(cls, value):
        # Convert the input value to lowercase for case-insensitive matching
        value = str(value).lower()
        for member in cls:
            if member.value.lower() == value:
                return member
        # If no match is found, raise a ValueError
        raise ValueError(f"'{value}' is not a valid {cls.__name__}")
# --- 1. FastAPI App and Input Validation ---

And now you can create other enums that extend this enum to get the case-insensitive effect:

class ScriptLength(CaseInsensitiveEnum):
    short = "short"  # ~50-75 words
    medium = "medium"  # ~100-150 words
    long = "long"  # ~200-250 words

Now you can safely parse the enum no matter the case:

case insensitive parsing of string to enum in python

Obviously, you can get creative and create a catch-all for string value that cannot converge into a value after case conversion.

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