FastAPI 0.126.0 移除了對 Pydantic v1 的支援，但在一段時間內仍支援 `pydantic.v1`。

/// warning

Pydantic 團隊自 **Python 3.14** 起，已停止在最新的 Python 版本中支援 Pydantic v1。

這也包含 `pydantic.v1`，在 Python 3.14 及以上版本不再支援。

如果你想使用最新的 Python 功能，就需要確保使用 Pydantic v2。

///

如果你的舊 FastAPI 應用仍使用 Pydantic v1，這裡會示範如何遷移到 Pydantic v2，並介紹 **FastAPI 0.119.0** 中可協助你逐步遷移的功能。

## 官方指南 { #official-guide }

```bash
.
├── app                  # "app" is a Python package
│   ├── __init__.py      # this file makes "app" a "Python package"
│   ├── main.py          # "main" module, e.g. import app.main
│   ├── dependencies.py  # "dependencies" module, e.g. import app.dependencies
│   └── routers          # "routers" is a "Python subpackage"
│   │   ├── __init__.py  # makes "routers" a "Python subpackage"

Ви робите це за допомогою стандартних сучасних типів Python.

Вам не потрібно вивчати новий синтаксис, методи чи класи конкретної бібліотеки тощо.

Лише стандартний **Python**.

Наприклад, для `int`:

```Python
item_id: int
```

або для складнішої моделі `Item`:

```Python
item: Item
```

...і з цим єдиним оголошенням ви отримуєте:

I tested several ideas in the most popular Python editors: PyCharm, VS Code, Jedi based editors.

By the last [Python Developer Survey](https://www.jetbrains.com/research/python-developers-survey-2018/#development-tools), that covers about 80% of the users.

    "Programming Language :: Python :: 3 :: Only",
    "Programming Language :: Python :: 3.10",
    "Programming Language :: Python :: 3.11",
    "Programming Language :: Python :: 3.12",
    "Programming Language :: Python :: 3.13",
    "Programming Language :: Python :: 3.14",
    "Topic :: Internet :: WWW/HTTP :: HTTP Servers",
    "Topic :: Internet :: WWW/HTTP",
]
dependencies = [
    "starlette>=0.46.0",
    "pydantic>=2.9.0",

      langs: ${{ steps.show-langs.outputs.langs }}
      commands: ${{ steps.show-langs.outputs.commands }}
    steps:
      - uses: actions/checkout@v6
      - name: Set up Python
        uses: actions/setup-python@v6
        with:
          python-version-file: ".python-version"
      - name: Setup uv
        uses: astral-sh/setup-uv@v7
        with:
          cache-dependency-glob: |
            pyproject.toml
            uv.lock

# Code blocks { #code-blocks }

Some text

```python
# This is a sample Python code block
def hello_world():
    # Comment with indentation
    print("Hello, world!")  # Print greeting
```

Some more text

Missing code block...

And more text

```console
// Use the command "live" and pass the language code as a CLI argument
$ python ./scripts/docs.py live es

然后我们对 `users` 模块进行相同的操作。

我们也可以像这样导入它们：

```Python
from app.routers import items, users
```

/// info | 信息

第一个版本是「相对导入」：

```Python
from .routers import items, users
```

第二个版本是「绝对导入」：

```Python
from app.routers import items, users
```

要了解有关 Python 包和模块的更多信息，请查阅[关于 Modules 的 Python 官方文档](https://docs.python.org/3/tutorial/modules.html)。

///

# Code blocks { #code-blocks }

Some text

```python
# This is a sample Python code block
def hello_world():
    # Comment with indentation
    print("Hello, world!")  # Print greeting
```

Some more text

```toml
# Extra line
# This is a sample TOML code block
title = "TOML Example"  # Title of the document
```

And more text

```console
// Use the command "live" and pass the language code as a CLI argument

* `datetime.datetime`:
    * A Python `datetime.datetime`.
    * In requests and responses will be represented as a `str` in ISO 8601 format, like: `2008-09-15T15:53:00+05:00`.
* `datetime.date`:
    * Python `datetime.date`.
    * In requests and responses will be represented as a `str` in ISO 8601 format, like: `2008-09-15`.
* `datetime.time`:
    * A Python `datetime.time`.