fastapi

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• SKILL.md
• dependencies.md · references/
• other-tools.md · references/
• streaming.md · references/

SKILL.md (first lines)

# FastAPI

Official FastAPI skill to write code with best practices, keeping up to date with new versions and features.

## Use the `fastapi` CLI

Run the development server on localhost with reload:

```bash
fastapi dev
```


Run the production server:

```bash
fastapi run
```

### Add an entrypoint in `pyproject.toml`

FastAPI CLI will read the entrypoint in `pyproject.toml` to know where the FastAPI app is declared.

```toml
[tool.fastapi]
entrypoint = "my_app.main:app"
```

### Use `fastapi` with a path

When adding the entrypoint to `pyproject.toml` is not possible, or the user explicitly asks not to, or it's running an independent small app, you can pass the app file path to the `fastapi` command:

```bash
fastapi dev my_app/main.py
```

Prefer to set the entrypoint in `pyproject.toml` when possible.

## Use `Annotated`

Always prefer the `Annotated` style for parameter and dependency declarations.

It keeps the function signatures working in other contexts, respects the types, allows reusability.

### In Parameter Declarations

Use `Annotated` for parameter declarations, including `Path`, `Query`, `Header`, etc.:

```python
from typing import Annotated

from fastapi import FastAPI, Path, Query

app = FastAPI()


@app.get("/items/{item_id}")
async def read_item(
    item_id: Annotated[int, Path(ge=1, description="The item ID")],
    q: Annotated[str | None, Query(max_length=50)] = None,
):
    return {"message": "Hello World"}
```

instead of:

```python
# DO NOT DO THIS
@app.get("/items/{item_id}")
async def read_item(
    item_id: int = Path(ge=1, description="The item ID"),
    q: str | None = Query(default=None, max_length=50),
):
    return {"message": "Hello World"}
```

### For Dependencies

Use `Annotated` for dependencies with `Depends()`.

Unless asked not to, create a new type alias for the dependency to allow re-using it.

```python
from typing import Annotated

from fastapi import Depends, FastAPI

app = FastAPI()


def get_current_user():
    return {"username": "johndoe"}


CurrentUserDep = Annotated[dict, Depends(get_current_user)]


@app.get("/items/")
async def read_item(current_user: CurrentUserDep):
    return {"message": "Hello World"}
```

instead of:

```python
# DO NOT DO THIS
@app.get("/items/")
async def read_item(current_user: dict = Depends(get_current_user)):
    return {"message": "Hello World"}
```

## Do not use Ellipsis for *path operations* or Pydantic models

Do not use `...` as a default value for required parameters, it's not needed and not recommended.

Do this, without Ellipsis (`...`):

```python
from typing import Annotated

From maulik-sharma/Major-Project-PR1107, MIT.

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