Python - Virtualenv , python 3?

Question

Seems everyone recommends virtualenv for multiple python versions (on osx), but does it even work with python 3.0? I downloaded it, and it doesn't seem to.. And I don't really understand how it works, Can you 'turn on' on env at a time or something? What I want is to leave the system python 2.5 (obviously), and to have python 3.1.1 with subversion pygame to write my own stuff, and python 2.6 with normal stable pygame to use to run other things, like pygame games downloaded from pygame.org. Any help on how to accomplish that? Thanks.

OK I realized virtualenv is not what I'm looking for.

Answer 1

Your use case doesn't actually need virtualenv. You just need to install several different Python versions.

Answer 2

It's an old question by now, but I found it myself on top of google search for the answer, and I don't think the answers provided are what people are looking for.

As I understand it you want to create different virtual environments with different Python versions?

This is very easy, and you only need virtualenv itself.

For, say, a Python 3:

$ virtualenv -p python3 p34env

(...)
New python executable in p34env/bin/python3.4
Also creating executable in p34env/bin/python
Installing setuptools, pip...done.

$ source p34env/bin/activate

(p34env)$ python -V
Python 3.4.2

(p34env)$ deactivate 
$

You use the source command to activate the venv, and deactivate to - you guessed it - deactivate it. Notice the prompt changes to indicate the env.

For your system's standard version of Python you just skip the -p python3 argument, and you can use the argument to point to any version you want given a path.

The last argument is the name (p34env) and you can make as many as you like, just give them different names.

Answer 3

virtualenv is designed to create isolated environments of a Python environment. The trick to using it with multiple Python instances is to either install virtualenv into each of the Python versions you want to use it with, for example:

/usr/bin/easy_install-2.6 virtualenv
/usr/local/bin/easy_install virtualenv
sudo port install py26-virtualenv

or to invoke it with the intended Python version, for example:

/usr/bin/python2.6 virtualenv.py ENV
/usr/local/bin/python2.6 virtualenv.py ENV
/opt/local/bin/python2.5 virtualenv.py ENV

So, as such, it doesn't directly solve the problem (particularly acute on OS X) of which Python you want to work with. There are various ways to deal with that issue: use absolute paths to the intended Python (as in the above examples), define shell aliases, carefully manage the $PATH search order, among others.

At the moment, AFAIK, virtualenv is not supported with Python 3 because, among other things, setuptools (the magic behind easy_install) is not yet supported on Python 3, although there is work in progress towards a solution for that.

BTW, many people use Doug Hellman's virtualenvwrapper to simplify use of virtualenv.

Answer 4

For me virtualenv3 works very well. I also have pypi.python.org/pypi/distribute installed. That also works with the mentioned www.doughellmann.com/docs/virtualenvwrapper/ . I've only tested that on Linux though.

Answer 5

Not sure if I understood you correctly, but here goes :)

I don't know about OS X, but in Linux you can install both 2.6 and 3. Then you can either specify to use python25 or python3, or change the /usr/bin/python symlink to the version you want to use by default.