[Zope3-dev] Re: Google SoC Project

[Tarek Ziadé]

Jim Fulton wrote:

>> out of curiosity, what are the things that make a reload not robust ?
>> is it just a matter of dependencies or it's deeper ?
>
>
> I was hoping that someone else would answer this directly. :)
> Shane did largely answer it, but I'll try to be more direct and
> concise:
>
> When you reaload a module, the module source is recompiled and
> executed.  Values defined in the new version overwrite values of
> the same name in the old version.  This has lots of implications:
>
> - Client modules that imported names using from:
>
>     from oldmodule import somename
>
>   Don't see the update.
>
> - Instances of classes defined in the module remain instances
>   of the old classes.
>
> - Writable global data is overwritten.  This is a common source
>   of subtle bugs when a module defines a registry or cache.
>
> There are probably other interesting things I'm not thinking of.
>
> There are ways of working around these issues, but they require
> special techniques that aren't always followed or can be defeated.
>
> Jim
>
Ok, thanks for the explanation

Tarek