bpo-30938: Add pdb command to show user-owned variables

[FrontSide]

Add debugger commands "who" and "whos" - similar to the
ones from ipython - to list the names of user-owned variables (who)
and user-owned variable names together with the variable type
and the assigned value.

Manually tested.

Example:

>>> import pdb 
>>> x = 1 
>>> y = {'key': 'value'}
>>> pdb.set_trace()
(Pdb) who
x       y 
(Pdb) whos
Variable        Type    Data/Info
------------------------------  
x               int     1   
y               dict    {'key': 'value'}

[the-knights-who-say-ni]

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[mention-bot]

@FrontSide, thanks for your PR! By analyzing the history of the files in this pull request, we identified @birkenfeld, @tim-one and @Yhg1s to be potential reviewers.

[FrontSide]

Just added my GitHub username to my bugs.python.org profile there.

[blueyed]

Interesting!
Please add tests for it.

[iritkatriel]

David, this has been open for a while. Are you planning to work on the tests? If not I wouldn't mind trying.

[FrontSide]

Go for it @iritkatriel. Would love to see this getting merged : )

[iritkatriel]

Is it deliberate that who shows globals and locals while whos shows only locals?

[FrontSide]

@iritkatriel mhh, no sounds like a bug. I'd say it should probably always be globals.

[iritkatriel]

I have some changes to your code in https://github.com/iritkatriel/cpython/tree/whos (I'm not sure how to make a PR into this branch. Also, this branch needs to be rebased).

The changes are (1) refactor out the bit that creates the user vars list. (2) I changed the code that iterates over them in whos so that globals are correctly shadowed by locals.

For whos, I think there is a lot more work to do to make it render neatly when the values are large.

I also added a test for who (but not for whos).

[github-actions]

This PR is stale because it has been open for 30 days with no activity.

[MaxwellDupre]

Nice addition, but I would expect a NEWS entry and a change to the docs so that user are aware.

[iritkatriel]

Closing since this was abandoned by the OP.