How to properly achieve different example(s) for same type/model per endpoint?

[jeremyschiemann]

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Example Code

from fastapi import FastAPI, Path
from typing import Annotated
from copy import deepcopy

app = FastAPI()

item_id_type = Annotated[str, Path(description='This is my Item ID', ge=10, le=50, example=12)]
item_id_type_b = deepcopy(item_id_type)
item_id_type_b.__metadata__[0].example = 17


@app.get('/route_a')
def operation_a(item_id: item_id_type) -> str
  if item_id == 17:
    raise ValueError('item with id 17 doesnt support this operation')
  return f'id: {item_id}'

@app.get('/route_a')
def operation_b(item_id: item_id_type_b) -> str:
  if item_id == 12:
    raise ValueError('item with id 12 doesnt support this operation')
  return f'id: {item_id}

Description

I'm trying to have a single type that represents an item ID but make different endpoints use a different example.

rightnow I'm using a workaround by copying the original type and then mutate the example like so:

item_id_type_b = deepcopy(item_id_type)
item_id_type_b.__metadata__[0].example = 17

Is there a better way to have a single type/model with its validations etc but use different examples per endpoint?
The only other option I see is copy/pasting the Path-definition resulting in a lot of code duplication.

Everything else i tied either didn't work or overrides the Path-definition entirely.

Operating System

Other

Operating System Details

WSL (ubuntu) on Windows 10

FastAPI Version

0.109.2

Pydantic Version

2.5.3

Python Version

3.11.4

Additional Context

No response

[YuriiMotov]

This seems to be working:

from typing import Annotated

from fastapi import FastAPI, Path

app = FastAPI()

item_id_type = Annotated[
    str,
    Path(description="This is my Item ID", ge=10, le=50, example=1),
]


@app.get("/route_a")
def operation_a(item_id: Annotated[item_id_type, Path(example=12)]) -> str:
    if item_id == 17:
        raise ValueError("item with id 17 doesnt support this operation")
    return f"id: {item_id}"


@app.get("/route_b")
def operation_b(item_id: Annotated[item_id_type, Path(example=17)]) -> str:
    if item_id == 12:
        raise ValueError("item with id 12 doesnt support this operation")
    return f"id: {item_id}"

BTW, ge and le are not working for str type fields. And you need to include {item_id} to the paths:

from typing import Annotated

from fastapi import FastAPI, Path

app = FastAPI()

item_id_type = Annotated[
    int,
    Path(description="This is my Item ID", ge=10, le=50, example=1),
]


@app.get("/route_a/{item_id}")
def operation_a(item_id: Annotated[item_id_type, Path(example=12)]) -> str:
    if item_id == 17:
        raise ValueError("item with id 17 doesnt support this operation")
    return f"id: {item_id}"


@app.get("/route_b/{item_id}")
def operation_b(item_id: Annotated[item_id_type, Path(example=17)]) -> str:
    if item_id == 12:
        raise ValueError("item with id 12 doesnt support this operation")
    return f"id: {item_id}"