Set Up Python with CentOS Linux

 Python is a widely used interpreted language that has brought professionalism to the world of coding scripted applications on Linux (and other operating systems). Where Perl was once the industry standard, Python has surpassed Perl in many respects.

Some strengths of Python versus Perl are −

• Rapid progression in refinement

• Libraries that are standard to the language

• Readability of the code is thought out in language definition

• Many professional frameworks for everything from GUI support to web-development

Python can do anything Perl can do, and in a lot of cases in a better manner. Though Perl still has its place amongst the toolbox of a Linux admin, learning Python is a great choice as a skill set.

The biggest drawbacks of Python are sometimes related to its strengths. In history, Python was originally designed to teach programming. At times, its core foundations of "easily readable" and "doing things the right way" can cause unnecessary complexities when writing a simple code. Also, its standard libraries have caused problems in transitioning from versions 2.X to 3.X.

Python scripts are actually used at the core of CentOS for functions vital to the functionality of the operating system. Because of this, it is important to isolate our development Python environment from CentOS' core Python environment.

For starters, there are currently two versions of Python − Python 2.X and Python 3.X.

Both stages are still in active production, though version 2.X is quickly closing in on depreciation (and has been for a few years). The reason for the two active versions of Python was basically fixing the shortcomings of version 2.X. This required some core functionality of version 3.X to be redone in ways it could not support some version 2.X scripts.

Basically, the best way to overcome this transition is − Develop for 3.X and keep up with the latest 2.X version for legacy scripts. Currently, CentOS 7.X relies on a semi-current revision of version 2.X.

As of this writing, the most current versions of Python are − 3.4.6 and 2.7.13.

Don't let this confuse or draw any conclusions of Python. Setting up a Python environment is really pretty simple. With Python frameworks and libraries, this task is actually really easy to accomplish.

Before setting up our Python environments, we need a sane environment. To start, let's make sure our CentOS install is fully updated and get some building utilities installed.

Step 1 − Update CentOS.

[root@CentOS]# yum -y update

Step 2 − Install build utilities.

[root@CentOS]# yum -y groupinstall "development tools"

Step 3 − Install some needed packages.

[root@CentOS]# yum install -y zlib-dev openssl-devel sqlite-devel bip2-devel

Now we need to install current Python 2.X and 3.X from source.

• Download compressed archives
• Extract files
• Compile source code

Let's start by creating a build directory for each Python install in /usr/src/

[root@CentOS]# mkdir -p /usr/src/pythonSource

Now let's download the source tarballs for each −

[root@CentOS]# wget https://www.python.org/ftp/python/2.7.13/Python-2.7.13.tar.xz
[root@CentOS]# wget https://www.python.org/ftp/python/3.6.0/Python-3.6.0.tar.xz

Now we need to extract each from the archive.

Step 1 − Install xz-libs and extract the tarballs.

[root@CentOS]# yum install xz-libs
[root@CentOS python3]# xz -d ./*.xz
[root@CentOS python3]# ls
Python-2.7.13.tar  Python-3.6.0.tar
[root@CentOS python3]#

Step 2 − Untar each installer from its tarball.

[root@CentOS]# tar -xvf ./Python-2.7.13.tar
[root@CentOS]# tar -xvf ./Python-3.6.0.tar

Step 3 − Enter each directory and run the configure script.

[root@CentOS]# ./configure --prefix=/usr/local 
root@CentOS]# make altinstall

Note − Be sure to use altinstall and not install. This will keep CentOS and development versions of Python separated. Otherwise, you may break the functionality of CentOS.

You will now see the compilation process begins. Grab a cup of coffee and take a 15minute break until completion. Since we installed all the needed dependencies for Python, the compilation process should complete without error.

Let's make sure we have the latest 2.X version of Python installed.

[root@CentOS Python-2.7.13]# /usr/local/bin/python2.7 -V 
Python 2.7.13
[root@CentOS Python-2.7.13]#

Note − You will want to prefix the shebang line pointing to our development environment for Python 2.X.

[root@CentOS Python-2.7.13]# cat ver.py  
#!/usr/local/bin/python2.7 
import sys 
print(sys.version)

[root@CentOS Python-2.7.13]# ./ver.py 
2.7.13 (default, Jan 29 2017, 02:24:08)
[GCC 4.8.5 20150623 (Red Hat 4.8.5-11)]

Just like that, we have separate Python installs for versions 2.X and 3.X. From here, we can use each and utilities such as pip and virtualenv to further ease the burden of managing Python environments and package installation.