Could not find and pre-evaluate ui.run(). Starting interactive mode without auto-reload.

[me21]

I've repeated the sample from your website in my project in PyCharm:

from nicegui import ui

ui.label('Hello NiceGUI!')
ui.button('BUTTON', on_click=lambda: ui.notify('button was pressed'))

ui.run()

However, when I debug it, I get the following output:

"C:\Users\azarubkin\Documents\Python Projects\evolve_web\venv\Scripts\python.exe" "C:\Program Files\JetBrains\PyCharm 2021.2.3\plugins\python\helpers\pydev\pydevd.py" --multiprocess --qt-support=auto --client 127.0.0.1 --port 63893 --file "C:/Users/azarubkin/Documents/Python Projects/evolve_web/nicegui_main.py"
Connected to pydev debugger (build 221.5591.52)
Could not find and pre-evaluate ui.run(). Starting interactive mode without auto-reload.
C:/Users/azarubkin/Documents/Python Projects/evolve_web/venv/lib/site-packages/justpy
Module directory: C:\Users\azarubkin\Documents\Python Projects\evolve_web\venv\lib\site-packages\justpy, Application directory: C:\Users\azarubkin\Documents\Python Projects\evolve_web
JustPy ready to go on http://0.0.0.0:8080

How can I fix this so that I get hot reloading?

[me21]

I've found that the cause is due to how configuration object is filled, by parsing the source of the file being run, and in case of debugging in PyCharm, this is pydevd.py, not nicegui_main.py.
If I run without debugging, no such message appears, but another warning pops up:

The --reload flag should not be used in production on Windows.

[falkoschindler]

That's caused by the way NiceGUI pre-evaluates the ui.run command while evaluating from nicegui import ui. It has to know, whether it should start a uvicorn server with the reload flag (which will in turn evaluate the main script) or if the main script is evaluated first and the server is started by calling ui.run. Therefore it evaluates the call stack in config.py at around line 37 to find your main script. When using interactive interpreters or debuggers, they appear in the call stack and have to be filtered. We tried to do that for some IDEs, but surely missed some.

In your case, I assume we can simply add "pydevd.py" to the list of excluded_strings. Maybe you can try that out for me, since I have currently no PyCharm installed. If something is weird, it might help to print all f.filename within the for-loop to see the whole call stack. Thanks!

[me21]

I had to add 'pydevd.py' and '_pydev_execfile.py'. Thanks for the suggestion.

[falkoschindler]

Great! I'm adding these filenames in version 0.7.28.