[Tutor] Debugging skills

[dn]

On 6/01/24 02:56, Mats Wichmann wrote:
> On 1/4/24 14:58, dn via Tutor wrote:
> 
>>>> Interestingly the paper book version of my tutorial has a chapter on
>>>> debugging. However, I've never got round to adding that chapter
>>>> to the online version. I probably should...
>>>
>>> That would be cool.
> 
> while we're nattering on a whole range of sort-of-debugging topics, 
> here's something I've occasionally wondered about, when a beginner has 
> written something that makes sense only to them, not to the Python 
> interpreter.  Regexes are confusing, so there are several websites (see 
> for example regex101.com) where you can enter your "code" (regex) and as 
> it's interpreted, will show you an explanation in words in a separate 
> pane.  Does anyone know if there's a similar thing for Python code? 
> "This is what you wrote actually means to the interpreter".  Ones I know 
> about (like at Programiz, w3schools, online-python) don't attempt the 
> explanation part.  It's not something that's likely to be useful for 
> very many cases, but I could see where in the beginning there might be 
> some benefit...

It's a lot easier to build such 'checkers' when working with a small and 
bounded system, than with something as broad as Python.

Am thinking that the best tool to diagnose when a trainee's mental-model 
diverges from Python's way of working, is the interpreter. Work has been 
invested in recent versions to improve err.msgs/diagnostics. Of course, 
this will never be perfect, and it is a bug-bear of learners of all 
languages that the diagnosis may be incorrect, and thus a red-herring.

The concern is valid, and particularly in a self-teach/remote-learner 
situation where asking someone for help may be problematic.

Reprising earlier conversation, I fear that the attempt to go too far, 
too fast, will lead to, or certainly more-frequently evidence this problem.

My solution (in other topics) is to show multiple examples of (correct) 
working-code and discuss how each works, in order to create and 
reinforce the requisite mental-model. Then ask the trainees to solve a 
(very) similar problem - for which many have the wit to copy a suitable 
example, and edit from there. Seems to work!

As previously-mentioned, and echoed by @Roel, PythonTutor does go some 
way to illustrating what's happening under-the-hood. No, pdb is not so 
good (IMHO) and thus even less-so in a training environment. PyCharm's 
debugger does a reasonable job, by stepping-through and showing values 
as they change in a dashboard-like manner - but it doesn't draw the 
'pretty pictures' per PythonTutor or Thonny.

-- 
Regards,
=dn