Execution failed (No module named tkinter)
Hello, the first question is how to open an existing file? you can write in the editor and you can save, but how to open it?
Now the second question, I tried a relatively simple Python script, and it supposedly completed the compilation successfully (of course, not creating a single file), but in response to the "Execute" button, it gave an error "Execution failed! (Took911ms). ln0: ImportExcept: No module named tkinter ".
Naturally, this module is present in the installed python version.

Hi! I think tkinter simply isn't included in the IronPython runtime. Take a look at Compilers/Python, and feel free to open a Pull Request including tkinter, I'll happily merge it.
Also, to open files I think you can simply use drag and drop or the Ctrl + O shortcut, or rightclick the source file and select Open with Fiddle.