------------
- used to isolate python installations when there are conflicting packages
between applications
- example scenario: app1 needs module version 1 but app2 needs module version 2
- each virtual environment has its own set of directory tree for python
installation
- module that creates a virtual environment is `venv`
Using Virtual Environments
--------------------------
Old hard way | 1. install first the module `venv`
2. create a virtual environment (tutorial-env is the directory and will be created if it doesn't exist)
# python -m venv tutorial-env
3. activate the virtual environment
# source tutorial-env/bin/activate
4. your prompt will include the virtual environment
(tutorial-env) $ python Python 3.5.1 (default, May 6 2016, 10:59:36) ... >>> import sys >>> sys.path ['', '/usr/local/lib/python35.zip', ..., '~/envs/tutorial-env/lib/python3.5/site-packages'] >>> |
Easy new way | 1. create virtual environment (by default this will inject python2 in your virtualenv) merrell@myubuntu:~$ mkvirtualenv project1 New python executable in /home/merrell/.virtualenvs/project1/bin/python Installing setuptools, pip, wheel...done. virtualenvwrapper.user_scripts creating /home/merrell/.virtualenvs/project1/bin/predeactivate virtualenvwrapper.user_scripts creating /home/merrell/.virtualenvs/project1/bin/postdeactivate virtualenvwrapper.user_scripts creating /home/merrell/.virtualenvs/project1/bin/preactivate virtualenvwrapper.user_scripts creating /home/merrell/.virtualenvs/project1/bin/postactivate virtualenvwrapper.user_scripts creating /home/merrell/.virtualenvs/project1/bin/get_env_details (project1) merrell@myubuntu:~$
2. Install a package inside your virtual environment without affecting other libraries (project1) merrell@myubuntu:~$ pip install click Collecting click Downloading click-6.7-py2.py3-none-any.whl (71kB) 100% |████████████████████████████████| 71kB 30kB/s Installing collected packages: click Successfully installed click-6.7 (project1) merrell@myubuntu:~$
3. Get out of the virtualenv (project1) merrell@myubuntu:~$ deactivate merrell@myubuntu:~$
4. View available virtualenvs merrell@myubuntu:~$ lsvirtualenv project1 ========
merrell@myubuntu:~$
5. You may also create a python 3 virtualenv merrell@myubuntu:~$ mkvirtualenv -p python3 py3 Running virtualenv with interpreter /usr/bin/python3 Using base prefix '/usr' New python executable in /home/merrell/.virtualenvs/py3/bin/python3 Also creating executable in /home/merrell/.virtualenvs/py3/bin/python Installing setuptools, pip, wheel...done. virtualenvwrapper.user_scripts creating /home/merrell/.virtualenvs/py3/bin/predeactivate virtualenvwrapper.user_scripts creating /home/merrell/.virtualenvs/py3/bin/postdeactivate virtualenvwrapper.user_scripts creating /home/merrell/.virtualenvs/py3/bin/preactivate virtualenvwrapper.user_scripts creating /home/merrell/.virtualenvs/py3/bin/postactivate virtualenvwrapper.user_scripts creating /home/merrell/.virtualenvs/py3/bin/get_env_details (py3) merrell@myubuntu:~$ |
Setup and Installation
----------------------
pip install virtualenv virtualenvwrapper --user
cp ~/.bashrc ~/.bashrc.orig
echo "export WORKON_HOME=~/.virtualenvs" >> ~/.bashrc
echo "source virtualenvwrapper.sh" >> ~/.bashrc
Troubleshooting
---------------
Selinux in virtualenv | Ansible needs "libselinux-python" package to be installed on source is installed using pip and run it inside a virtualenv, tasks like those that uses "template" module will fail with the following error:
"msg": "Aborting, target uses selinux but python bindings (libselinux-python) aren't installed!"
This is because system wide selinux module is not inherited by virtualenv and you cannot install selinux module via pip.
Using global python enables importing of selinux module: >>> import selinux >>> selinux.is_selinux_enabled() 1 >>>
But not inside virtualenv. >>> import selinux Traceback (most recent call last): File "<stdin>", line 1, in <module> ImportError: No module named selinux >>> Workaround is to copy the selinux modules from system wide path to your virualen's site-packages.
~$ rpm -ql libselinux-python /usr/lib64/python2.7/site-packages/_selinux.so /usr/lib64/python2.7/site-packages/selinux /usr/lib64/python2.7/site-packages/selinux/__init__.py /usr/lib64/python2.7/site-packages/selinux/__init__.pyc /usr/lib64/python2.7/site-packages/selinux/__init__.pyo /usr/lib64/python2.7/site-packages/selinux/audit2why.so ~$ cp /usr/lib64/python2.7/site-packages/_selinux.so ~/.virtualenvs/testenv/lib/python2.7/site-packages ~$ cp -Rp /usr/lib64/python2.7/site-packages/selinux ~/.virtualenvs/testenv/lib/python2.7/site-packages ~$ sudo chown -R ansible:ansible ~/.virtualenvs/testenv/lib/python2.7/site-packages |
