Why doesn't Python (error msg) tell me WHAT the actual (arg) values are ?

[avi.e.gross at gmail.com]

We have been supplying many possible reasons or consequences for why the
implementation of python does not do what the OP wants and even DEMANDS.

I am satisfied with knowing it was because they CHOSE NOT TO in some places
and maybe not in others. It is nice to see some possible reasons, but
something as simple as efficiency or needing to complicate the code in
something used regularly, might be enough for now.

But to comment on what Michael T. and Dave N. have been saying, newcomers
often have no clue of what can happen so their questions may sound quite
reasonable.

So what happens if you create a large data structure, so some operation that
fails, catch the error and save the variables involved in an exception and
throw that onward and perhaps the program keeps running? There is now a
pointer to the large data structure in the exception object, or even a copy.
If that exception is not discarded or garbage collected, it can remain in
memory indefinitely even if the original string was expected to be removed,
replaced, or garbage collected. Some modern features in R such as generators
will stay alive infinitely and retain their state in between calls for a
next item.

You can end up with memory leaks that are not trivial to solve or that may
mysteriously disappear when an iterable has finally been consumed and all
the storage it used or pointed at can be retrieved, as one example.

A more rational approach is to realize that python has multiple levels of
debugging and exceptions are one among many. They are not meant to solve the
entire problem but just enough to be helpful or point you in some direction.
Yes, they can do more.

And, FYI, I too pointed this person at the Tutor list and I see no sign they
care how many people they make waste their time with so many mainly gripes.
I personally now ignore any post by them.
-----Original Message-----
From: Python-list <python-list-bounces+avi.e.gross=gmail.com at python.org> On
Behalf Of Michael Torrie
Sent: Thursday, February 23, 2023 10:32 PM
To: python-list at python.org
Subject: Re: Why doesn't Python (error msg) tell me WHAT the actual (arg)
values are ?

On 2/23/23 01:08, Hen Hanna wrote:
>  Python VM  is seeing an "int" object (123)   (and telling me that)   ...
so it should be easy to print that "int" object 
> What does  Python VM    know ?   and when does it know it ?
It knows there is an object and its name and type.  It knows this from the
first moment you create the object and bind a name to it.
> it seems like  it is being playful, teasing (or mean),    and   hiding
the ball from me

Sorry you aren't understanding.  Whenever you print() out an object, python
calls the object's __repr__() method to generate the string to display.  For
built-in objects this is obviously trivial. But if you were dealing an
object of some arbitrary class, there may not be a
__repr__() method which would cause an exception, or if the __repr__()
method itself raised an exception, you'd lose the original error message and
the stack trace would be all messed up and of no value to you.  Does that
make sense?  Remember that Python is a very dynamic language and what might
be common sense for a built-in type makes no sense at all for a custom type.
Thus there's no consistent way for Python to print out the information you
think is so simple.
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