[Pythonmac-SIG] Namespace conflict with WebWare and PyObjC / Import safety (Was: how do I use twisted cfreactor?)

[Bob Ippolito]

On Jan 14, 2005, at 17:14, Bob Ippolito wrote:

> On Jan 14, 2005, at 16:56, Kevin Dangoor wrote:
>
>> Bob Ippolito wrote:
>>
>>> (Kevin sent me the test off-list, and I took a look at it).
>>>
>>> I'm not sure exactly why your example crashes (somehow a retain 
>>> message gets sent to a dead or non-object), however, the problem is 
>>> that you are using an import statement from inside the 
>>> implementation of the action.  Don't do that.  Do your imports in 
>>> module level code.
>>
>> Wow. That was quick!
>>
>> I didn't realize that there was a gotcha with the imports. That was 
>> just a premature optimization, so I can easily avoid that :)
>>
>> Thanks for your help... that's certainly not the kind of thing I 
>> would have just guessed...
>
> I don't think there is typically a gotcha with imports, I've certainly 
> never seen this happen before, and I have done imports from 
> applicationDidFinishLaunching: (pygame, in particular) before.  I have 
> no idea if I should be blaming Cheetah, PyObjC or Python 2.3.0 
> (haven't tested with 2.4 or CVS), but I will try and remember to dig 
> in later.

I have traced the problem.  It is a two-parter:

(1) There is a module namespace conflict:
WebWare has a package named WebKit
PyObjC has a package named WebKit

(2) Cheetah.Servlet checks to see if WebWare's WebKit is available, and 
ends up importing PyObjC's WebKit.

(3) For whatever reason, it is not safe to import the WebKit wrapper 
from inside of an action (unless it's already imported, of course).  
Now this issue I will have to look further into.

---
So apparently it's more or less undefined behavior if you have both 
WebWare and PyObjC installed!  Fun :)

-bob