[Neuroimaging] Technical details managing Python versions and packages.

Yaroslav Halchenko lists at onerussian.com
Mon Aug 3 17:49:01 CEST 2015

On Mon, 03 Aug 2015, Matthew Brett wrote:

> > And only then, when I hit the situation that some package is not yet
> > available from (Neuro)Debian, I usually create a virtualenv which
> > complements system-wide collection (virtualenv --system-site-packages)
> > and use its pip to install additional packages ideally by specifying
> > them within requirements.txt (pip install -r requirements.txt) so I
> > could later reproduce the same virtualenv.

> As a matter of interest - how do you set up fresh environments to test in?

it depends what I am testing. If I am testing Debian package of a
module, tests are ran as part of the build process, and that one happens
in a clean environment which is created usually as a chroot'ed
environment with only build-depends installed (as specified in
debian/control).  No virtualenv involved.

I also have a set of chroots available locally so I could quickly switch
to any given release of debian/ubuntu using schroot.

then for 'semi-clean/mixed' environments I just use virtualenv (as
described, i.e. with some packages coming from the system installation
again), and now started to use tox more, which again preinstalls
me those virtualenv's

> One of the big advantages of virtualenv for this is you can test a
> fresh install with no packages other than the stock pip / setuptools.

yes -- for fresh packages, use virtualenv/tox.
again as overlay on top of system wide installed ones.

Why mixing up with system-wide -- because I want to test as when
eventually this package would  get provided on a debian system, so with
those other packages as available from the repository, not what at this
given day available from pypi.

> You can also easily junk a set of installs with:

> rmvirtualenv my-env

> How do you do that?

not sure on specifics of this question -- "rm -rf my-env"? ;)  My
virtualenvs aren't usually long-lived.

Yaroslav O. Halchenko, Ph.D.
http://neuro.debian.net http://www.pymvpa.org http://www.fail2ban.org
Research Scientist,            Psychological and Brain Sciences Dept.
Dartmouth College, 419 Moore Hall, Hinman Box 6207, Hanover, NH 03755
Phone: +1 (603) 646-9834                       Fax: +1 (603) 646-1419
WWW:   http://www.linkedin.com/in/yarik        

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