[Python-Dev] dir() in inspect.py ?

[Christian Tismer]

On 21.05.12 07:52, Stefano Taschini wrote:
> On 21 May 2012 03:36, Guido van Rossum <guido at python.org 
> <mailto:guido at python.org>> wrote:
>
>     [...]
>
>     I have to agree with Christian that inspect.py is full of hacks and
>     heuristics that would be fine in a module that's part of a user's app
>     or even in a library, but stand out as brittle or outright unreliable
>     in a stdlib module. Basically, you can't trust that inspect.py will
>     work. I've seen various occasions (sorry, can't remember details)
>     where some function in it outright crashed when given a slightly
>     unusual (but not unreasonable) argument. It might be a nice project
>     for a new contributor to improve this situation.
>     [...]
>
>
> An example that crashes is
>
>      >>>  def f(l, (x, y)):
>      ...    sup = max(u*x + v*y for u, v in l)
>      ...    return ((u, v) for u, v in l if u*x + v*y == sup)
>      >>>  inspect.getargspec(f)
>
> See http://bugs.python.org/issue14611 . I did submit a patch, a few 
> weeks ago.

Nice finding, not related to dir() usage but very useful to know.
I looked over test_inspect.py a bit, which is quite big and has many
tests, although very little references to reported bugs, and this
opcode combination was obviously missing in the test cases.

Did not find your patch yet (no time), but hope you added an extra
testcase with explicit reference to the bug reported.

inspect is very nice and useful in many cases, but sometimes not. Instead
of using things like currentframe() I have a look and write my own version
because the convenience is too little compared to an extra import and
dependency. And although currentframe() is mentioned in test_inspect,
I cannot find any direct testcase for it that really calls this function.

Admittedly a trivial case, but it is one reason, besides dissed dir() usage,
that makes me think of 'suspect' ;-)

Instead, I'd love to use inspect as the basis to write reliable, portable
code, because its abstraction hides implementation details nicely.
I think we have reached when things like sys._getframe() are declared
as deprecated.

""" This is no longer recommended to use. Use inspect.currentframe 
instead """

cheers - chris

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