# How to Install Python 3 on CentOS 7.7 using yum/source and set as Default

By

Charl Cronje

• The CentOS 7 Linux distribution includes Python 2 by default. However, Python 2 has reached its EOL on January 1, 2020.
• In this tutorial, we are going to take a look at how to get up and running with Python 3 on a CentOS 7 server.
• These instructions assume that your server has CentOS release 7.7.

• In CentOS 7 releases prior to 7.7, it was necessary to make Python 3 available for installation by setting up third-party repositories, such as the IUS repository, because the CentOS base repository did not provide a Python 3 package. Thankfully, as of CentOS 7.7, Python 3 is available in the base package repository!

[root@centos7 ~]# yum update -y

[root@centos7 ~]# yum install -y python3

That’s it! Python 3 is now installed! Another helpful idea to consider is that PIP, the Python package manager for Python 3, is installed alongside the Python 3 package, so we don’t have to worry about that as an additional installation step.

• Install development tools and some prerequisite packages.

[root@centos7 ~]# yum groupinstall -y "Development Tools" && yum install gcc openssl-devel bzip2-devel libffi-devel -y

[root@centos7 ~]# alternatives --install /usr/bin/python python /usr/bin/python2 50
[root@centos7 ~]# alternatives --install /usr/bin/python python /usr/bin/python3.6 60
[root@centos7 ~]# alternatives --config python

In order to ensure that Python 3 is in fact installed and useable, we can drop into a Python 3 shell by running the following command.

[root@centos7 ~]# python
Python 3.6.8 (default, Aug  7 2019, 17:28:10) 
[GCC 4.8.5 20150623 (Red Hat 4.8.5-39)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>

You should see the version of Python 3 installed on your system as well as a change in the command prompt characters.

Yum package manager usage python2 by default so after you make python3 as default the yum will break.

[root@centos7 ~]# yum install ftp
  File "/usr/bin/yum", line 30
    except KeyboardInterrupt, e:
                            ^
SyntaxError: invalid syntax
Fix it here -

To fix this change the python interpreter to /usr/bin/python2.7 in two files

[root@centos7 ~]# cat /usr/bin/yum
#!/usr/bin/python2.7
[root@centos7 ~]# cat /usr/libexec/urlgrabber-ext-down
#!/usr/bin/python2.7

• Installing Python 3 via the Yum package manager is by far the simplest way to get the job done. However, in some cases, you might want to have the most recent version of Python available and that’s where a source installation can come in handy.

• In order to install Python 3 from source, we are going to need to ensure that some prerequisite packages are installed on our system.

[root@centos7 ~]# yum install gcc openssl-devel bzip2-devel libffi-devel -y

Next, we need to grab the version of Python we want. The following command will pull down the latest stable version of Python 3.8 as of the writing of this article.

[root@centos7 ~]# curl -O https://www.python.org/ftp/python/3.8.1/Python-3.8.1.tgz

Now we need to extract the file.

[root@centos7 ~]# tar -xzf Python-3.8.1.tgz

Now that it’s extracted, let’s change into the resultant directory.

[root@centos7 ~]# cd Python-3.8.1/

Next, we need to prepare to compile Python from source.

[root@centos7 Python-3.8.1]# ./configure --enable-optimizations

Finally, we are going to use the following command to finish off the installation, without replacing the default system Python on our system.

[root@centos7 Python-3.8.1]# make altinstall

Compiling code from source takes a little while, but once that’s finished, we can test out our new Python 3 version by running the following command.

[root@centos7 Python-3.8.1]# python3.8

• Much like before when we installed Python 3.6 via Yum, we are dropped into a Python shell that outputs the version we are currently using.
• Python 3.8.1 (default, Dec 27 2019, 17:12:30)

[GCC 4.8.5 20150623 (Red Hat 4.8.5-39)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>
``

Done