reloading modules and isinstance()

[Diez B. Roggisch]

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.

reload() can be convenient, if you know its limitiations. But it has 
some, and they are deeply rooted in the way python works. So you gonna 
have to live with it.


Diez