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Comment by afarrell | Hacker News Reader

If you want to switch back and forth between python2 and python3, one option is to install miniconda (like Anaconda, but with just the package manager) as your Python distribution and create a python2 environment (conda create --name=myproject-py2 python=2.7 && source activate myproject-py2) that you can then pip install the python2-only libraries into. Then, when your libraries support Python3, create a new Python3 environment and install them into that (conda env export > environment.yml && conda create --name=myproject-py3 python=3.4 && conda env update --name=myproject-py3 --file=environment.yml && source activate myproject-py3)

See http://conda.io

Disclosure: conda is open-source, but I work for company that sponsors most of the development.

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I believe virtualenv (with/without virtualenvwrapper) is most widely used. Not sure if there are any advantages/disadvantages compared to conda tho.

https://virtualenv.pypa.io/en/latest/ https://virtualenvwrapper.readthedocs.org/en/latest/

One disadvantage of conda/anaconda is that you can't, or are discouraged from using virtualenv with conda/anaconda.

I use Anaconda on Win7, like it a lot, but I haven't figured out how to use, say, the python 2 that comes with anaconda alongside the python 2 that comes from python.org. I've looked around, haven't really understood what I should be looking at for that. But whatever it is, it isn't virtualenv if you use Anaconda.

One disadvantage of conda/anaconda is that you can't, or are discouraged from using virtualenv with conda/anaconda.

True, but conda has its own virtual environments that work quite nicely. You can make a new one with conda create and switch between them with activate/deactivate. You even get the same sort of interaction with pip (for the packages you want that aren't in conda or binstar), and I've been able to use e.g. Emacs packages that expect to work with virtualenv and have (mostly) had success using conda's envs instead.

Yep, and your answer is the sort of answer I see all around, including on their forum. I haven't figured out the doc.

How would you use conda's environments to switch between Andconda's python 2 and python.org's python 2?

Why would you want to do that? If you're using anaconda or miniconda, you should be using Continuum Analytics' builds of python, not python.org python.

Because I want to use Anaconda and its infrastructure, but skeptical people in my circle would want to see that whatever was built will run on the version of python that they would download (which would not be Anaconda).

"Why would you want to ..." answers are generally pretty frustrating. It's a big universe with a very large possible set of individual circumstances.

Can this be done?

If you're building conda packages then the only possible consumer is other users of miniconda or anaconda.

I'm not sure "whatever was built" refers to in this case. Some kind of app? Of course you can use anaconda for normal library or application development, since there's functionally no difference between Continuum Analytics' python builds and the python.org python build.

I want to run the following, using either of Anaconda or python.org python 2, on the same machine depending on the whim of the day:

  C:> python -c "print 'hello'"
  hello

all version trouble disappears with https://github.com/yyuu/pyenv

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