Lab: Ansible, Python3, and Virtualenvs on CentOS and RHEL

Ansible, Python
Lab: Ansible, Python3, and Virtualenvs on CentOS and RHEL

Overview

Virtualenvs make considerable sense, discussed in more depth here, in any complex python or Ansible environment. In the HOWTO, or lab, we’ll quickly get a python 3 virtualenv up and running on a RHEL or CentOS system.

This article is written making use of one of Red Hat’s Lab Environments running RHEL, in this case on AWS, however this should run fine on CentOS standalone systems. Obviously your repo configurations may vary so adjust to taste, I’ve assumed a pretty minimal install and have opted for CentOS available repos. If you want to recreate the system used to develop this then check out our industrial grade Ansible Cloud Deployer, deploying thousand of instances a week, agnosticd (and please join the growing community of contributors.)

Note
 This is a Preview lab and is aimed at development and test environments NOT PRODUCTION. For Production Ansible infrastructure I strongly recommend using Red Hat Enterprise Linux and official yum packages throughout. In a Lab situation however pip and virtualenvs offer tremendous flexibility

  1. With many of the systems I’ve worked with I’ve found the repos for python3 on both CentOS and RHEL are often not enabled. In this case follow the step below though you can always skip straight to Step 2.

    $ sudo yum -y install https://centos7.iuscommunity.org/ius-release.rpm
    Note
    		 I’m using a CentOS rpm above as this will work with both CentOS and RHEL. This so those of you who are using CentOS can complete this HOWTO.

  2. Now we can install both python3 and pip3

    $ sudo yum -y install python36u python36u-pip
    Note
    		 At this point I’d probably sym-link them to /usr/local/bin. Be careful with making any changes in /bin itself as many pieces of software expect and use the default python. 
    ln -s /bin/python3.6 /usr/local/bin/python
ln -s /bin/pip3.6 /usr/local/bin/pip3

  3. Optional, python 3.6 comes with support for virtualenvs so there is no longer a need to pip install virtualenv. However I strongly recommend installing, and configuring, virtualenvwrapper. I find it indispensable and rarely, if ever, create or use virtualenvs without it. I plan to cover this in depth in my next article.

    pip3.6 install virtualenvwrapper

  4. Either set the following ENV vars from the command line or better still set them in your ~/bashrc, or equivalent and source ~/.bashrc

    export WORKON_HOME=$HOME/.virtualenvs
export VIRTUALENVWRAPPER_PYTHON=/bin/python3.6

  5. Next source virtualenvwrapper`s `/bin/virtualenvwrapper.sh. Again it makes sense to put this in your ~/.bashrc or in my case often ~/.zshrc.

    source /bin/virtualenvwrapper.sh

Making our first Python 3 virtualenv

Now we’ve completed all the pre-requisites to create, use, and destroy Python 3 virtualenvs at will. So let’s create a simple virtualenv with the latest and greatest Ansible.

  1. Make the virtualenv with the mkvirtualenv function we acquired when we sourced /bin/virtualenvwrapper.sh earlier.

    $ mkvirtualenv ansible-py3
mkvirtualenv ansible-py3
Using base prefix '/usr'
  No LICENSE.txt / LICENSE found in source
New python executable in /home/tok/.virtualenvs/ansible-py3/bin/python3.6
Also creating executable in /home/tok/.virtualenvs/ansible-py3/bin/python
Installing setuptools, pip, wheel...
done.
virtualenvwrapper.user_scripts creating /home/tok/.virtualenvs/ansible-py3/bin/predeactivate
virtualenvwrapper.user_scripts creating /home/tok/.virtualenvs/ansible-py3/bin/postdeactivate
virtualenvwrapper.user_scripts creating /home/tok/.virtualenvs/ansible-py3/bin/preactivate
virtualenvwrapper.user_scripts creating /home/tok/.virtualenvs/ansible-py3/bin/postactivate
virtualenvwrapper.user_scripts creating /home/tok/.virtualenvs/ansible-py3/bin/get_env_details

<output omitted>

(ansible-py3) $

  2. The prompt change tells us we’ve successfully made, and activated, our first python 3 virtualenv. Validate it is configured as expected.

    (ansible-py3) $ pip list
Package    Version
---------- -------
pip        19.1.1
setuptools 41.0.1
wheel      0.33.4
(ansible-py3) $ type python
python is /home/tok/.virtualenvs/ansible-py3/bin/python
(ansible-py3) $ type pip
pip is /home/tok/.virtualenvs/ansible-py3/bin/pip
(ansible-py3) $ python --version
Python 3.6.7
(ansible-py3) $ type pip
pip is /home/tok/.virtualenvs/ansible-py3/bin/pip

  3. If everything is as expected then install Ansible

    (ansible-py3) $  pip install ansible
Collecting ansible
  Downloading https://files.pythonhosted.org/packages/17/c9/
d379b76ecaa42f4ee08b01c365e9ed1be0b302ff8a26eef120d481b144fa/
ansible- 2.8.0.tar.gz (14.3MB)
     |████████████████████████████████| 14.3MB 37.9MB/s

<... output truncated ...>
Successfully built ansible PyYAML pycparser
Installing collected packages: MarkupSafe, jinja2, PyYAML, pycparser,
cffi, asn1crypto, six, cryptography, ansible

Successfully installed MarkupSafe-1.1.1 PyYAML-5.1 ansible-2.8.0
asn1crypto-0.24.0 cffi-1.12.3 cryptography-2.6.1 jinja2-2.10.1
pycparser-2.19 six-1.12.0

  4. Confirm the virtualenv is configured as expected,

    (ansible-py3) $ pip list
Package      Version
------------ -------
ansible      2.8.0
asn1crypto   0.24.0
cffi         1.12.3
cryptography 2.6.1
Jinja2       2.10.1
MarkupSafe   1.1.1
pip          19.1.1
pycparser    2.19
PyYAML       5.1
setuptools   41.0.1
six          1.12.0
wheel        0.33.4

So now you have a working python3 virtualenv with the latest and greatest Ansible installed. If you are not familiar with creating and activating virtualenvs I recommend taking a look at these related resources below.

However if you are in a hurry then workon <virtualenv-name>, deactivate,and pip install will get you started. Or the pip cheatsheet.