运行ReactPy示例脚本遇‘RuntimeError: No built-in server...’错误的原因

我运行ReactPy入门示例命令：

python -c "import reactpy; reactpy.run(reactpy.sample.SampleApp)"

时，触发了RuntimeError: No built-in server implementation installed.错误。该示例来自一篇入门教程，且python -m http.server可正常运行。

完整堆栈信息如下：

python -c "import reactpy; reactpy.run(reactpy.sample.SampleApp)"


2023-06-11T02:37:17+0300 | WARNING | The `run()` function is only intended for testing during development! To run in production, consider selecting a supported backend and importing its associated `configure()` function from `reactpy.backend.<package>` where `<package>` is one of ['starlette', 'fastapi', 'sanic', 'tornado', 'flask']. For details refer to the docs on how to run each package.
Traceback (most recent call last):
  File "/opt/homebrew/lib/python3.11/site-packages/reactpy/backend/default.py", line 59, in _default_implementation
    implementation = next(all_implementations())
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
StopIteration

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/opt/homebrew/lib/python3.11/site-packages/reactpy/backend/utils.py", line 37, in run
    app = implementation.create_development_app()
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/lib/python3.11/site-packages/reactpy/backend/default.py", line 28, in create_development_app
    return _default_implementation().create_development_app()
           ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/lib/python3.11/site-packages/reactpy/backend/default.py", line 62, in _default_implementation
    raise RuntimeError("No built-in server implementation installed.")

原因分析 #

• ReactPy的reactpy.run()方法依赖后端Web框架实现，默认安装的ReactPy仅包含核心库，不会自动附带任何后端依赖
• 缺少官方支持的后端框架（如Starlette、FastAPI、Flask等），导致无法启动开发服务器
• python -m http.server是Python内置静态文件服务器，和ReactPy需要的动态Web后端不属于同一类服务，因此它能正常运行不代表满足ReactPy的依赖要求

解决方法 #

安装任意一个ReactPy支持的后端框架即可，示例如下：

• 安装Flask：

pip install flask

• 或安装Starlette：

pip install starlette

安装完成后重新运行示例命令即可正常启动。

内容的提问来源于stack exchange，提问作者jeremy_rutman