reloading modules and isinstance()

[Jean-Paul Calderone]

On Thu, 06 Dec 2007 12:21:01 +0100, "Diez B. Roggisch" <deets at nospam.web.de> wrote:
>Tlis schrieb:
>> On 5 Dec, 13:18, Steven D'Aprano <st... at REMOVE-THIS-
>> cybersource.com.au> wrote:
>>> On Tue, 04 Dec 2007 15:41:48 +0100, Diez B. Roggisch wrote:
>>>> You just discovered one reason why reload() is a bad idea and IMHO
>>>> shouldn't be used at all - as tempting it might be.
>>> I disagree -- I find reload() extremely useful for interactively testing
>>> modules. But I would never dream of using it in production code!
>>>
>>> --
>>> Steven.
>>
>> Please note, that I was using the 'Reload modules' functionality of
>> the software system in use, rather than the reload() function
>> directly. I admit, though, that in the background it just may call
>> reload() ...
>>
>> With all the problems of the reload() function, I still hope, that
>> there should be possible to write a safe module 'reloader', that would
>> fix the references, as required (e.g. by changing the
>> variable.__class__ references). This should be provided by every
>> serious Python development environment.
>
>Wishful thinking. If I do
>
>foo = {}
>foo['some_key'] = somemodule.SomeClass
>
>somewhere in my code, how do you suppose is reload(somemodule) to know
>where in all the world I keep references to that class? Thus it would
>essentially have to scan all references to anything, all list contents,
>all class-properties, all everything. Which is not feasible.

Who says it isn't feasible?

http://twistedmatrix.com/trac/browser/trunk/twisted/python/rebuild.py

Jean-Paul