[Python-Dev] PEP 376 - Open questions

[P.J. Eby]

At 11:28 PM 7/8/2009 -0400, Eric Smith wrote:
>>Eventually, I'd like PEP 376 to support system packagers too. So 
>>for example, if you did "apt-get install python-pyqt4", then 
>>running "pip install python-pyqt4" should return without installing 
>>anything .. as RECORD will be part of the .deb previously 
>>installed. As for generating the RECORD file, I vote for generating 
>>it during install time (w/ absolute paths).
>
>I think we should explicitly not support this. What if pip and 
>apt-get (or rpm, or others) install the same package in different 
>places because of system conventions (/usr vs. /usr/local vs. /opt, 
>say)? There's no way we're ever going to get this right, and it's 
>not worth complicating our lives over it.
>
>Seriously: Is there some real world use case I'm missing? Does any 
>existing install system support this?

The use case described above is supported right now by easy_install 
and pip; it doesn't require a RECORD file, though.  An .egg-info file 
or an .egg-info directory with a PKG-INFO is enough to prevent 
duplicate installation.

I don't know how pip handles file overwrites; easy_install OTOH never 
overwrites anything that's not in an .egg or a .pth.