logo-teal-vector.svg...

## What makes a dependency

Up to now you have seen dependencies declared as functions.

But that's not the only way to declare dependencies (although it would probably be the more common).

The key factor is that a dependency should be a "callable".

A "**callable**" in Python is anything that Python can "call" like a function.

        self.example = example
        self.include_in_schema = include_in_schema
        self.openapi_examples = openapi_examples
        kwargs = dict(
            default=default,
            default_factory=default_factory,
            alias=alias,
            title=title,
            description=description,
            gt=gt,
            ge=ge,
            lt=lt,
            le=le,
            min_length=min_length,

        item_id: Annotated[int, Path(title="The ID of the item to get")],
    ):
        return {"item_id": item_id}
    ```
    """
    return params.Path(
        default=default,
        default_factory=default_factory,
        alias=alias,
        alias_priority=alias_priority,
        validation_alias=validation_alias,
        serialization_alias=serialization_alias,
        title=title,
        description=description,

      - name: Setup tmate session
        uses: mxschmitt/action-tmate@v3
        if: ${{ github.event_name == 'workflow_dispatch' && github.event.inputs.debug_enabled == 'true' }}
        with:
          limit-access-to-actor: true
      - uses: docker://tiangolo/latest-changes:0.3.0
      # - uses: tiangolo/latest-changes@main
        with:
          token: ${{ secrets.GITHUB_TOKEN }}
          latest_changes_file: docs/en/docs/release-notes.md

* **FastAPI**:
    * The same way that Starlette uses Uvicorn and cannot be faster than it, **FastAPI** uses Starlette, so it cannot be faster than it.

      - name: Dump GitHub context
        env:
          GITHUB_CONTEXT: ${{ toJson(github) }}
        run: echo "$GITHUB_CONTEXT"
      - name: Decide whether the needed jobs succeeded or failed
        uses: re-actors/alls-green@release/v1
        with:

    It clearly inspired Uvicorn and Starlette, that are currently faster than Sanic in open benchmarks.

!!! check "Inspired **FastAPI** to"
    Find a way to have a crazy performance.

// The env var no longer exists afterwards
$ python main.py

Hello World from Python
```

</div>

!!! tip
    You can read more about it at <a href="https://12factor.net/config" class="external-link" target="_blank">The Twelve-Factor App: Config</a>.

### Types and validation

// 现在它可以读取环境变量

Hello Wade Wilson from Python

// 之后环境变量不再存在
$ python main.py

Hello World from Python
```

</div>

!!! tip
    您可以在 <a href="https://12factor.net/config" class="external-link" target="_blank">Twelve-Factor App: Config</a> 中阅读更多相关信息。

### 类型和验证

这些环境变量只能处理文本字符串，因为它们是外部于 Python 的，并且必须与其他程序和整个系统兼容（甚至与不同的操作系统，如 Linux、Windows、macOS）。