homepage

I think all the lines involved in a multi-line expression should be reported.
Take for example this simple code:
 x = [int(c, 16)
 for c in '0123456789ABCDEFG'
 if c.isdigit() or c.isupper()]
With Python 2 the traceback is:
Traceback (most recent call last):
 File "deleteme.py", line 3, in <module>
 if c.isdigit() or c.isupper()]
ValueError: invalid literal for int() with base 16: 'G'
Which is not very helpful, because you don't see the int() call that is causing the error in the first place and you don't see where the G comes from.
Incidentally, for this specific case, the traceback is a bit better on Python3:
Traceback (most recent call last):
 File "deleteme.py", line 2, in <module>
 for c in '0123456789ABGDEF'
 File "deleteme.py", line 3, in <listcomp>
 if c.isdigit() or c.isupper()]
ValueError: invalid literal for int() with base 16: 'G'
But this still misses the int() call.
IMHO it would be better to have something like:
 Traceback (most recent call last):
 File "deleteme.py", lines 1-3, in <module>
 x = [int(c, 16)
 for c in '0123456789ABCDEFG'
 if c.isdigit() or c.isupper()]
ValueError: invalid literal for int() with base 16: 'G'
If this is rejected for some reason, I think printing the first line -- rather than the last -- would still be an improvement, because in most of the cases the first line contains more information (e.g. the name of the function with a multi-line list of args, a raise/assert with the name of the exception and part of the message, the operation done for each element of a genexp/listcomp).