Python : how to use virtualenv

Reference

http://www.dabapps.com/blog/introduction-to-pip-and-virtualenv-python/

http://blog1.erp2py.com/2011/07/virtualenv.html

Small tips.

With virtualenv, you can create python virtual environment separately for each projects.

install virtualenv

root@ubuntu:~# apt-cache install python-pip root@ubuntu:~# pip install virtualenv # virtualenv --version 1.11.6

create python virtual environment under dest_dir1 directory.

root@ubuntu:/home/hattori/Python_works# virtualenv dest_dir1 New python executable in dest_dir1/bin/python Installing setuptools, pip...done.

python environment has been created under dest_dir1.

root@ubuntu:/home/hattori/Python_works# ls dest_dir1/ bin  include  lib  local root@ubuntu:/home/hattori/Python_works# ls dest_dir1/bin/ activate      activate.fish     easy_install      pip   pip2.7  python2 activate.csh  activate_this.py  easy_install-2.7  pip2  python  python2.7

use this env and install requests module within that environment

python env has changed from “/usr/bin/python” to “dest_dir1/bin/python”

root@ubuntu:/home/hattori/Python_works# which python /usr/bin/python root@ubuntu:/home/hattori/Python_works# source dest_dir1/bin/activate (dest_dir1)root@ubuntu:/home/hattori/Python_works# (dest_dir1)root@ubuntu:/home/hattori/Python_works# which python /home/hattori/Python_works/dest_dir1/bin/python (dest_dir1)root@ubuntu:/home/hattori/Python_works# which pip /home/hattori/Python_works/dest_dir1/bin/pip (dest_dir1)root@ubuntu:/home/hattori/Python_works# pip install requests

“activate” file is a bash script, so you can check that to know the script executes what kind of things.

# unset irrelevant variables deactivate nondestructive VIRTUAL_ENV="/home/hattori/Python_works/dest_dir1" export VIRTUAL_ENV _OLD_VIRTUAL_PATH="$PATH" PATH="$VIRTUAL_ENV/bin:$PATH" export PATH

exit this env

(dest_dir1)root@ubuntu:/home/hattori/Python_works# deactivate root@ubuntu:/home/hattori/Python_works# root@ubuntu:/home/hattori/Python_works# which python /usr/bin/python

You can use different python version.

root@ubuntu:/home/hattori/Python_works# virtualenv -p /usr/bin/python3.4 dest_dir2 Running virtualenv with interpreter /usr/bin/python3.4 Using base prefix '/usr' New python executable in dest_dir2/bin/python3.4 Also creating executable in dest_dir2/bin/python Installing setuptools, pip...done. (dest_dir2)root@ubuntu:/home/hattori/Python_works# which python /home/hattori/Python_works/dest_dir2/bin/python (dest_dir2)root@ubuntu:/home/hattori/Python_works# python --version Python 3.4.0 (dest_dir2)root@ubuntu:/home/hattori/Python_works# deactivate root@ubuntu:/home/hattori/Python_works#