[Python-Dev] Re: More informative error messages

[Alex Martelli]

On Tuesday 07 October 2003 02:33 am, Greg Ewing wrote:
> Alex Martelli <aleaxit at yahoo.com>:
> > Python's error messages are slowly but surely getting better in that,
> > instead of just saying that something (e.g.) "must be int" (and
> > leaving the coder in the dark about WHAT it was instead)
>
> While we're on the subject of error messages, I'd like to
> point out another one that could be improved. Often one
> sees things like
>
>   TypeError: foo() takes exactly 1 argument (2 given)
>
> In the case where foo() is a method of some class, and there
> are various versions of foo() defined in various superclasses,
> it's sometimes hard to tell exactly *which* foo it was trying
> to call. It would be much more useful if the module and
> class names were included in the error message, e.g.
>
>   TypeError: MyStuff.SomeClass.foo() takes exactly 1 argument (2
> given)

A perennial beginners' confusion (recently highlighted in a c.l.py thread
whose subject claimed that Python can't count;-) is about that "number
of arguments given" number: one calls zoop.bleep() and is told bleep
"takes exactly 2 arguments (1 given)" when one is sure that one has
given no argument at all (and should give exactly 1) -- the implied 'self'
causing the beginners' confusion.  It seems to me that, if we work on these
messages, we may be able to distinguish the bound-method case into

TypeError: bound method bleep() of Zoop instance takes exactly 1
argument (0 given)

or some such...


Alex