[Python-ideas] Have REPL print less by default

[Random832]

On Wed, Apr 20, 2016, at 14:25, Franklin? Lee wrote:
> Example:
>     File "<stdin>", line 1, in f
>     File "<stdin>", line 1, in g
>     [Mutually recursive calls hidden: f (300), g (360)]
>     File "<stdin>", line 1, in h
>     File "<stdin>", line 1, in f
>     File "<stdin>", line 1, in g
>    [Mutual-recursive calls hidden: f (103), g (200)]
>   RuntimeError: maximum recursion depth exceeded
>   [963 calls hidden. Call _full_ex() to print full trace.]
>
> Or maybe the second f and g are also folded into the second hidden
> bit. And maybe it checks line numbers when deciding whether to print
> explicitly (but not when folding).
>
> Would that output make indirect infinite recursion more difficult for
> you to debug?

You know what would make complicated infinite recursion easier to debug?
The arguments.

Is there a reliable way to determine what in f_locals correspond to
arguments? My toy example below only works for named positional
arguments.

def magic(frame):
    code = frame.f_code
    fname = code.co_name
    argcount = code.co_argcount
    args = code.co_varnames[:argcount]
    values = tuple(frame.f_locals[a] for a in args)
    result = '%s%r' % (fname, values)
    if len(result) > 64:
        return fname + '(...)'
    return result

Maybe even tokenize the source line the error occurred on and print any
other locals whose name matches any token on the line. I guess I'll
leave it to the bikeshed design committee and say: WIBNI tracebacks
printed relevant frame variables FSDO relevant?