Retrieve a field from a pydantic BaseModel which just has the given name or has the name set as an alias

pydantic_model_field.py

from typing import Optional
from pydantic import BaseModel


def get_model_field(model: BaseModel, field_name: str) -> Optional[str]:
    """
    Retrieves the field name from a Pydantic model based on a given field name or alias.

    This function searches the model's fields to find a match for the given field name or alias.
    If a match is found, it returns the actual field name. Since pydantic allows using
    the same alias for different fields, this function also checks for ambiguities,
    i.e., whether the given name or alias corresponds to multiple fields.
    In such cases, it raises a ValueError to indicate the ambiguity.
    """

    id_fields = [
        name
        for name, field in model.model_fields.items()
        if field_name in (name, field.alias)
    ]
    # pydantic allows the same alias for different fields
    if len(id_fields) > 1:
        raise ValueError("Ambiguous field '{field_name}' in model: {model}")
    return id_fields[0] if len(id_fields) else None