Dynamic StrEnums (Python's Enum inheriting from a str)

README.md

Why?

There may be a better way to do this, but this worked for me, and it is compatible with FastAPI's use of Enums.

Why not use the Enum functional API? (Animal = Enum('Animal', 'ANT BEE CAT DOG'))

This works if the fields are to be autogenerated using numbers, however to be useful with FastAPI Enum has to have values as str.

Are you sure?

Probably not, I would be glad to get an example of the above working, and compatible with FastAPI's Query Enums.

My use is:

post_orders: Ordering = {
    "created_time": "Oldest First",
    "comment_count": "Most Comments",
    "inverse_comment_count": "Fewest Comments",
}

PostOrders = create_strenum("PostOrders", svc_post.post_orders)

@router.get("/posts/", response_model=Posts)
async def get_all(
    order: PostOrders,
) -> Posts:
    pass

With the Enum functional example the FastAPI choices would be integers rather than the strings.

dyn_str_enum.py

from enum import Enum
from typing import Sequence


class StrEnum(str, Enum):
    pass


template = """class {name}(StrEnum):
    {fields}
"""


def create_strenum(name: str, keys: Sequence):
    """Dynamically create a StrEnum from a Sequence.
    >>> my_enum = create_strenum('Flowers', ('rose', 'violet'))
    >>> my_enum
    <enum 'Flowers'>
    >>> my_enum.__members__
    mappingproxy({'rose': <Flowers.rose: 'rose'>, 'violet': <Flowers.violet: 'violet'>})
    >>> my_enum.rose
    <Flowers.rose: 'rose'>
    """
    # implementation borrowed from Python's NamedTuple
    fields = "; ".join([f'{k}="{k}"' for k in keys])
    code = template.format(name=name, fields=fields)
    namespace = dict(__name__=f"dynstrenum_{name}", StrEnum=StrEnum)
    exec(code, namespace)
    return namespace[name]


if __name__ == "__main__":
    import doctest

    doctest.testmod()