In PDB, when you use "interact" to enter an interactive shell, the only way to exit that shell is to send an end-of-transmission (Ctrl+D) character. In some environments, such as Jupyter, this is awkward to do. Here is a StackOverflow post where a user encountered this issue:
https://stackoverflow.com/questions/47522316/exit-pdb-interactive-mode-from-jupyter-notebook/62546186

I think that the user should be able to type quit() in order to exit the interactive Python shell and go back to the PDB shell, similar to a regular interactive Python session. I think you should also support exit() because the Python shell supports that one as well (quit() and exit() do the same thing, I think the alias exists to help discoverability for new users).

I confirmed this issue on Python 3.6.9 and 3.8.3.

Both "exit" and "quit" and even just "q" quit the PDB interactive shell.

Serhiy: I'm referring to the interactive mode that can be entered by typing "interact" in PDB.

Here are reproduction instructions:
1. Run "python3" command.
2. In Python shell, type "import pdb; pdb.set_trace()".
3. In PDB shell, type "interact".

Now, in this "PDB InteractiveConsole" shell (I'm not sure what it's called), the only way to go back to PDB is to press Ctrl+D. If you type "quit()" or "exit()" it exits the entire Python process. If you type "q" it says "NameError: name 'q' is not defined".

In Jupyter, I get different (but still undesirable) behavior: "quit()" raises "NameError: name 'quit' is not defined" (and similar for "exit()").

I think "quit()"/"exit()" in these contexts should return you back to the PDB shell.

Thank you, now I understand the problem.

It is reasonable request, but a new feature can only be added in Python 3.10.