First check

• I added a very descriptive title to this issue.
• I used the GitHub search to find a similar issue and didn't find it.
• I searched the FastAPI documentation, with the integrated search.
• I already searched in Google "How to X in FastAPI" and didn't find any information.
• I already read and followed all the tutorial in the docs and didn't find an answer.
• I already checked if it is not related to FastAPI but to Pydantic.
• I already checked if it is not related to FastAPI but to Swagger UI.
• I already checked if it is not related to FastAPI but to ReDoc.
• After submitting this, I commit to:
  • Read open issues with questions until I find 2 issues where I can help someone and add a comment to help there.
  • Or, I already hit the "watch" button in this repository to receive notifications and I commit to help at least 2 people that ask questions in the future.
  • Implement a Pull Request for a confirmed bug.

Example

Here's a self-contained minimal, reproducible, example with my use case:

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/")
def read_root(q: str = Query(None)):
    return {"q": q.lower()}

Description

• Open the editor with that code, similar to many examples in the docs.
• It's quite probable that the editor won't complain that q can be None and that q.lower() could raise an error.

The solution you would like

I would like the examples in the docs to use Optional:

from typing import Optional

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/")
def read_root(q: Optional[str] = Query(None)):
    return {"q": q.lower()}

By using Optional the editor would be able to warn that q.lower() could raise an error if q is None.

Describe alternatives you've considered

To leave it as is.

Environment

• OS: [e.g. Linux / Windows / macOS]: All (docs)
• FastAPI Version [e.g. 0.3.0]: 0.56.0

To know the FastAPI version use:

python -c "import fastapi; print(fastapi.__version__)"

• Python version: All (docs)

To know the Python version use:

python --version

Additional context

I was waiting to first introduce Optional in the docs, but it was done in #1377 🎉

The new docs are here: https://fastapi.tiangolo.com/python-types/#optional

Now it's a good moment to update all the examples that have a default of None in all the docs to also use Optional.