closing a "nested" window with a button in PySimpleGUI and repeating this process

[Robby_PY]

I don't see how this could work.

if event == "Help":
        window_help.read()
        if event == "Cancel" or event == sg.WIN_CLOSED:
            break

To get to the "break" event has to equal "Help" and at the same time equal "Cancel" or sg.WIN_CLOSED. In you while loop you read one event at a time and process one event at a time.

You should also use elif to limit the code executed for each loop.

while True:
    event, values = window.read()
    if event == sg.WIN_CLOSED or event == 'Exit':
        break
     
    if event == 'Convert':  # Don't need elif here because of break
        seq=values['-IN-']
        rc= reverseComplement(seq)
        window['-OUTPUT-'].update(rc)
         
    elif event == "Help":
        window_help.read()

    elif event == "Cancel" or event == sg.WIN_CLOSED:
        window_help.close()

Thank you for your reply. I added the second if statement (below) with the reasoning that it would only apply to the "Help" window. So if "Help" is pressed, then a new window pop ups, with its own new event and if statement. That's how I used nested if statements before, so I thought it also worked like that in an event loop?

if event == "Help":
        window_help.read()
        if event == "Cancel" or event == sg.WIN_CLOSED:
            break

Thanks for rewriting the code. However, I still cannot close the Help window using the "Cancel" button. Also it is not possible to press Help twice. Any ideas how to solve this?