[Distutils] using pip to install an specific, older version

[Chris Jerdonek]

Hi Carl (or others),

On Mon, Apr 2, 2012 at 12:08 PM, Carl Meyer <carl at oddbird.net> wrote:
>
> Also, you may want to be aware that the -E flag is deprecated and is
> already removed in the latest pip release (1.1) because it does not
> handle isolated virtualenvs correctly. Instead, create a virtualenv and
> use the pip that is automatically installed inside it (virtualenv
> path/to/venv && path/to/venv/bin/pip install simplejson).

With regard to the above, if the recommended way to use pip is to use
it after calling virtualenv, then what is the recommended way to
invoke/install virtualenv for use from a global Python (e.g. from a
Python 3.2 installed via MacPorts).  Before, I would have installed
virtualenv by invoking pip with the -E flag.  But by the above that
approach is deprecated.

Also, does it matter whether virtualenv is run from Python 2 or Python
3?  In particular, can virtualenv run from both Python 2.x and Python
3.x create virtual environments based on both Python 2.x and Python
3.x?

Thanks,
--Chris