Implement %pdb support in notebooks

[rchiodo]

Assuming we have debugging working can %pdb also work? Not sure what this does at the moment, but user's have been asking for this.

[e13h]

The %pdb magic command automatically calls the interactive debugger when an exception is raised.

Source: https://ipython.readthedocs.io/en/stable/interactive/magics.html#magic-pdb

[dynamicwebpaige]

The %pdb magic command is often used with Jupyter and ipython notebooks as a recommended best practice; and there are several related questions on StackOverflow, about pdb + VS Code. The Python debugger is bundled with Python core - it definitely makes sense to support this.

• How to use pdb(Python debugger) in vscode IDE's debugger?
• Using the Python debugger with VS Code
• Set breakpoint in imported python module in vs code
• Break on error/exception with python remote development in Visual Studio Code (vscode)
• etc.

[DonJayamanne]

@int19h Does Python extension support %pdb for debugging? If yes, then I guess we can somehow try to get this working here as well.

[int19h]

debugpy doesn't have an interactive command mode like pdb does. Also, I think this command is hardcoded in the notebooks to specifically invoke pdb? If it's actually a hook that can invoke an arbitrary function, then having it invoke breakpoint() while running with debugpy attached should do the trick.

However, this particular scenario (breaking on exception) could be handled simply by running under debugger with User-uncaught Exceptions set to true.

[roblourens]

This is actually supported, via quick input

[rchiodo]

This is actually supported, via quick input

Do you have more details? %pdb is supposed to trap exceptions and show them in the debugger. At least I think that's how it works.

[roblourens]

When an exception occurs, I see a quick input show up which lets me enter pdb commands. In Jupyter lab, an input box appears below the cell for pdb commands. So it seems to work as well as Jupyter lab. I don't expect it to integrate with the vscode debugger or anything like that.

[micimize]

It seems unlikely to me that dropping into the full vscode from %pdb makes sense or is feasible – it would be confusing for %pdb not to invoke/work like pdb.

However, it might make sense to open a new issue to discuss/investigate a "drop into vscode debugger from running notebook" feature more thoroughly if that doesn't currently exist (or maybe better document how to set it up if it does).

[roblourens]

Can you explain more about what you're looking for? Debugging notebooks does exist with the "Debug cell" command

[micimize]

Ahh, ok – no that is perfect. For some reason it wasn't clear to me that Debug Cell used the existing notebook kernel.