[Python-Dev] Traceback style

[Guido van Rossum]

> On 02 May 2000, Ka-Ping Yee said:
> > I propose the following stylistic changes to traceback
> > printing:
> > 
> >     1.  If there is no function name for a given level
> >         in the traceback, just omit the ", in ?" at the
> >         end of the line.

Greg Ward expresses my sentiments:

> +0 on this: it doesn't really add anything, but it does neaten things
> up.
> 
> >     2.  If a given level of the traceback is in a method,
> >         instead of just printing the method name, print
> >         the class and the method name.
> 
> +1 here too: this definitely adds utility.
> 
> >     3.  Instead of beginning each line with:
> >         
> >             File "foo.py", line 5
> > 
> >         print the line first and drop the quotes:
> > 
> >             Line 5 of foo.py
> 
> -0: adds nothing, cleans nothing up, and just generally breaks things
> for no good reason.
> 
> >         In the common interactive case that the file
> >         is a typed-in string, the current printout is
> >         
> >             File "<stdin>", line 1
> >         
> >         and the following is easier to read in my opinion:
> > 
> >             Line 1 of <stdin>
> 
> OK, that's a good reason.  Maybe you could special-case the "<stdin>"
> case?  How about
> 
>    <stdin>, line 1
> 
> ?

I'd special-case any filename that starts with < and ends with > --
those are all made-up names like <string> or <stdin>.  You can display
them however you like, perhaps

  In "<string>", line 3

For regular files I'd leave the formatting alone -- there are tools
out there that parse these.  (E.g. Emacs' Python mode jumps to the
line with the error if you run a file and it begets an exception.)

--Guido van Rossum (home page: http://www.python.org/~guido/)