Use different Python version with virtualenv – Dev

The best answers to the question “Use different Python version with virtualenv” in the category Dev.

QUESTION:

I have a Debian system currently running with python 2.5.4. I got virtualenv properly installed, everything is working fine. Is there a possibility that I can use a virtualenv with a different version of Python?

I compiled Python 2.6.2 and would like to use it with some virtualenv. Is it enough to overwrite the binary file? Or do I have to change something in respect to the libraries?

ANSWER:

Since Python 3, the Python Docs suggest creating the virtual environment with the following command:

python3 -m venv <myenvname>

Please note that venv does not permit creating virtual environments with other versions of Python. For that, install and use the virtualenv package.


Obsolete information

The pyvenv script can be used to create a virtual environment

pyvenv /path/to/new/virtual/environment

but it has been deprecated since Python 3.6.

ANSWER:

Just use the --python (or short -p) option when creating your virtualenv instance to specify the Python executable you want to use, e.g.:

virtualenv --python=/usr/bin/python2.6 <path/to/new/virtualenv/>

N.B. For Python 3.3 or later, refer to The Aelfinn’s answer below.

ANSWER:

There is an easier way,

virtualenv venv --python=python2.7

Thanks to a comment, this only works if you have python2.7 installed at the system level (e.g. /usr/bin/python2.7).

Otherwise, if you are using homebrew you can use the path to give you what you want.

virtualenv venv --python=/usr/local/bin/python

You can find the path to your python installation with

which python

This will also work with python 3.

which python3
>> /usr/local/bin/python3
virtualenv venv --python=/usr/local/bin/python3

Ultimately condensing to:

virtualenv venv -p `which python`
virtualenv venv -p `which python3`

ANSWER:

These are the steps you can follow when you are on a shared hosting environment and need to install & compile Python from source and then create venv from your Python version. For Python 2.7.9. you would do something along these lines:

mkdir ~/src
wget http://www.python.org/ftp/python/2.7.9/Python-2.7.9.tgz
tar -zxvf Python-2.7.9.tgz
cd Python-2.7.9
mkdir ~/.localpython
./configure --prefix=$HOME/.localpython
make
make install

virtual env

cd ~/src
wget https://pypi.python.org/packages/5c/79/5dae7494b9f5ed061cff9a8ab8d6e1f02db352f3facf907d9eb614fb80e9/virtualenv-15.0.2.tar.gz#md5=0ed59863994daf1292827ffdbba80a63
tar -zxvf virtualenv-15.0.2.tar.gz
cd virtualenv-15.0.2/
~/.localpython/bin/python setup.py install
virtualenv ve -p $HOME/.localpython/bin/python2.7
source ve/bin/activate   

Naturally, this can be applicable to any situation where you want to replicate the exact environment you work and deploy on.