Extending StrEnum with _normalize_input_ for flexible value lookups

Ideas
1

Hi all,
I’d like to propose adding a method _normalize_input_ to StrEnum, allowing developers to define a custom input normalization before value lookup.

Why?

  • StrEnum requires exact string matches, making it cumbersome to handle case-insensitive or normalized value lookups.
  • Many real-world use cases require flexible matching (e.g. GraphQL, REST APIs, JSON)
  • Current workarounds require adding manual helpers methods, which are redundant across projects.

Proposal

A new class method _normalize_input_ (similarly to _generate_next_value_ or __new__) would allow developers to override how input values are processed before lookup.

class Colors(StrEnum):
    @staticmethod
    def _normalize_input_(cls, value):
        return value.lower()  # Allows case-insensitive lookup
    
    RED = auto()
    BLUE = auto()
    GREEN = auto()

Now, lookups apply _normalize_input_ before matching:

In [1]: Colors("Red")
Out[1]: <Colors.RED: 'red'>

In [2]: Colors("BLUE")
Out[2]: <Colors.BLUE: 'blue'>

In [3]: Colors("green")
Out[3]: <Colors.GREEN: 'green'>

Why this matters

  • Allows case-insensitive lookups and others pre-lookup transformations.
  • Integrates well with GraphQL, APIs and JSON configs.
  • Keeps Enums immutable while enabling flexible lookups.

Would love to hear your thoughts, is this something the community would find useful?
Thanks, Gonzalo

2

Enum._missing_ should work for this, right?

3

Thanks @Bullseye5995, you are right, _missing_ fully solve this problem