## Managing hermetic Python

To make sure that TensorFlow's build is reproducible, behaves uniformly across
supported platforms (Linux, Windows, MacOS) and is properly isolated from
specifics of a local system, we rely on hermetic Python (see
[rules_python](https://github.com/bazelbuild/rules_python)) for all build
and test commands executed via Bazel. This means that your system Python
installation will be ignored during the build and Python interpreter itself

```bash
clang-format <my_cc_file> --style=google > /tmp/my_cc_file.cc
diff <my_cc_file> /tmp/my_cc_file.cc
```

#### Python coding style

Changes to TensorFlow Python code should conform to
[Google Python Style Guide](https://github.com/google/styleguide/blob/gh-pages/pyguide.md)

Use `pylint` to check your Python changes. To install `pylint` and check a file
with `pylint` against TensorFlow's custom style definition:

```bash

You do that with standard modern Python types.

You don't have to learn a new syntax, the methods or classes of a specific library, etc.

Just standard **Python**.

For example, for an `int`:

```Python
item_id: int
```

or for a more complex `Item` model:

```Python
item: Item
```

...and with that single declaration you get:

        run: echo "$GITHUB_CONTEXT"
      - uses: actions/checkout@v6
      - name: Set up Python
        uses: actions/setup-python@v6
        with:
          python-version-file: ".python-version"
      - name: Install build dependencies
        run: pip install build
      - name: Build source distribution
        run: python -m build --sdist
      - name: Decompress source distribution
        run: |
          cd dist

      run: |
        echo Changed files: ${{ steps.get_file_changes.outputs.files }}
    - name: Set up Python 3.9
      uses: actions/setup-python@83679a892e2d95755f2dac6acb0bfd1e9ac5d548 # v6.1.0
      with:
        python-version: "3.9"
    - name: Install Python dependencies
      run: |
        python -m pip install --upgrade pip
        pip install pylint==2.13.9 numpy wheel
    - name: Run PyLint on changed files

        env:
          GITHUB_CONTEXT: ${{ toJson(github) }}
        run: echo "$GITHUB_CONTEXT"
      - uses: actions/checkout@v6
      - name: Set up Python
        uses: actions/setup-python@v6
        with:
          python-version: ${{ matrix.python-version }}
      - name: Setup uv
        uses: astral-sh/setup-uv@v7
        with:
          enable-cache: true
          cache-dependency-glob: |

以下のように書く代わりに:

//// tab | Python 3.10+

```Python
commons: Annotated[CommonQueryParams, Depends(CommonQueryParams)]
```

////

//// tab | Python 3.10+ 注釈なし

/// tip | 豆知識

可能であれば`Annotated`バージョンを使用することを推奨します。

///

```Python
commons: CommonQueryParams = Depends(CommonQueryParams)
```

////

...以下のように書きます:

//// tab | Python 3.10+

```Python

```JSON
{"item_id":3}
```

/// check

Notice that the value your function received (and returned) is `3`, as a Python `int`, not a string `"3"`.

So, with that type declaration, **FastAPI** gives you automatic request <dfn title="converting the string that comes from an HTTP request into Python data">"parsing"</dfn>.

///

## Data validation { #data-validation }

이전에 [Python 타입 소개](../python-types.md#type-hints-with-metadata-annotations)에서 `Annotated`를 사용해 매개변수에 메타데이터를 추가할 수 있다고 말씀드린 것을 기억하시나요?

이제 FastAPI에서 사용할 차례입니다. 🚀

다음과 같은 타입 어노테이션이 있었습니다:

```Python
q: str | None = None
```

여기서 `Annotated`로 감싸서 다음과 같이 만듭니다:

```Python
q: Annotated[str | None] = None
```

Pydantic이 사용하는:

* [`email-validator`](https://github.com/JoshData/python-email-validator) - 이메일 유효성 검사.

Starlette이 사용하는:

* [`httpx`](https://www.python-httpx.org) - `TestClient`를 사용하려면 필요.
* [`jinja2`](https://jinja.palletsprojects.com) - 기본 템플릿 설정을 사용하려면 필요.
* [`python-multipart`](https://github.com/Kludex/python-multipart) - `request.form()`과 함께 form <dfn title="HTTP 요청에서 온 문자열을 파이썬 데이터로 변환">"파싱"</dfn> 지원을 원하면 필요.