[Zope3-dev] System python for *development*? (Was: 3.3.0 tag broken by zc.catalog eggs?)

[Jim Fulton]

On May 21, 2007, at 1:39 AM, Martijn Pieters wrote:

> On 5/21/07, Gary Poster <gary at zope.com> wrote:
>> FWIW, I know zc.catalog but I'm certainly not an egg expert.  But
>> this message looks like you are maybe sharing a Python for various
>> installations.  Are you maybe using your system Python?  Generally
>> not advised for development work...try a standalone one?
>
> Come again? Using the system python when developing has always been
> fine;

No. It has never been fine for any aspect of development.  If you  
develop with your system Python and deploy with a custom environment,  
then you've added a variable that is different between the two  
environments.  Also, system Python's are often hobbled in ways that  
hurt development.

I sometimes get really weird error reports that are traced to system  
Pythons.  People who report problems to me that result from using a  
system Python make me angry and make me want to not answer their  
questions or otherwise help them any more.

System Python's have their place.  The are appropriate for casual  
Python users and small one-off scripts, but not much else IMO.

> the recommendation has only applied to deployment situations in
> the past. The point is that using a manual, dedicated build for a
> deployment gives you full control over tweaking that build for best
> performance without interfering with other users of the interpreter on
> the same system.
>
> I run dozens of development instances on my laptop, all with the same
> Macports python 2.4 installation. Creating a separate python build for
> each of these would be impractical, to say the least.

You don't have to use a Python per project to avoid the system  
Python. Just create a separate from-source installation and use that  
single installation. *Never* install anything into that  
installation.  Whether you are using eggs or not, any packages not  
included in a Python build from source should be managed in your  
project area.  Of course, eggs make this easier.

(IMO, it is also reasonable to include a Python build in a buildout,  
as long as it automated and as long as you don't mind the extra disk  
space usage and build time.  I prefer to use a shared clean Python  
myself.)

> However, it appears that the switch to eggs requires additional
> precautions to avoid your python system to be 'polluted' with various
> Zope3 packages. Perhaps we should recommend using workingenv for
> development work instead?

Yes, as others have mentioned, you should use workingenv or  
buildout.  (I wrote buildout because workingenv didn't provide enough  
control or automation for my needs.)

Jim
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