Flask APP-ValueError：信号仅在主线程中有效

Question

我尝试创建一个简单的flask 应用程序：

from flask import Flask

app = Flask(__name__)

if __name__ == '__main__':
  app.run()

但是当我添加调试时：

FLASK_APP = run.py
FLASK_ENV = development
FLASK_DEBUG = 1

我收到以下错误：

ValueError：信号仅在主线程中有效

这里是完整的堆栈跟踪

FLASK_APP = run.py
FLASK_ENV = development
FLASK_DEBUG = 1
In folder c:/MyProjectPath/api
c:\MyProjectPath\api\venv\Scripts\python.exe -m flask run
 * Serving Flask-SocketIO app "run.py"
 * Forcing debug mode on
 * Restarting with stat
 * Debugger is active!
 * Debugger PIN: 283-122-745
Exception in thread Thread-1:
Traceback (most recent call last):
  File "c:\appdata\local\programs\python\python37\Lib\threading.py", line 917, in _bootstrap_inner
    self.run()
  File "c:\appdata\local\programs\python\python37\Lib\threading.py", line 865, in run
    self._target(*self._args, **self._kwargs)
  File "c:\MyProjectPath\api\venv\lib\site-packages\flask_socketio\cli.py", line 59, in run_server
    return run_command()
  File "c:\MyProjectPath\api\venv\lib\site-packages\click\core.py", line 764, in __call__
    return self.main(*args, **kwargs)
  File "c:\MyProjectPath\api\venv\lib\site-packages\click\core.py", line 717, in main
    rv = self.invoke(ctx)
  File "c:\MyProjectPath\api\venv\lib\site-packages\click\core.py", line 956, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "c:\MyProjectPath\api\venv\lib\site-packages\click\core.py", line 555, in invoke
    return callback(*args, **kwargs)
  File "c:\MyProjectPath\api\venv\lib\site-packages\click\decorators.py", line 64, in new_func
    return ctx.invoke(f, obj, *args, **kwargs)
  File "c:\MyProjectPath\api\venv\lib\site-packages\click\core.py", line 555, in invoke
    return callback(*args, **kwargs)
  File "c:\MyProjectPath\api\venv\lib\site-packages\flask\cli.py", line 771, in run_command
    threaded=with_threads, ssl_context=cert)
  File "c:\MyProjectPath\api\venv\lib\site-packages\werkzeug\serving.py", line 812, in run_simple
    reloader_type)
  File "c:\MyProjectPath\api\venv\lib\site-packages\werkzeug\_reloader.py", line 267, in run_with_reloader
    signal.signal(signal.SIGTERM, lambda *args: sys.exit(0))
  File "c:\appdata\local\programs\python\python37\Lib\signal.py", line 47, in signal
    handler = _signal.signal(_enum_to_int(signalnum), _enum_to_int(handler))
ValueError: signal only works in main thread

Answer 1

您面临的问题与替换flask run命令的Flask-SocketIO软件包中的错误有关。因此，即使您不导入Flask-
SocketIO，也始终使用它。有几种解决方案：

1. 卸载Flask-SocketIO
2. 不使用flask run但运行程序的主文件
3. 禁用调试
4. 如果需要调试，请禁用自动加载 flask run --no-reload

引用Flask-SocketIO错误：问题817