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Delphi of Borland had this feature in their interactive Development Environment (IDE) .
For big SW projects it is essential, we knew it with the name: interactive debugging aid.

Are there (reliable) cross-compiler s that take your python code and generate (compiled C/C++) executables ?

You don't need executables that is the point. Everything runs from the source, both on Windows, Mac and Linux I believe.

So you just write into the console python filename.py or make the file itself an executable, this is done on linux by right click, and there setting it as executable and in the open with tab setting it as run so it becomes an executable. I don't know how on other OS it's done, I'm a Linux user.

Of course for GUI based code, there is the QT package: