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Friday, 14 October 2016

How to Install or Upgrade Python in Linux Systems

Hello readers! This is the second article of our tutorial series on Python - 'Python on Terminal' and in this article we will learn to install Python on your Linux system. In the last article of the series - Introduction to Python, I have mentioned that, Python is available on most of the Linux distributions, nowadays, normally Python version 2.x.x. Even though Python2 is still being used by 85%-90% industries worldwide, someone might want to try his hands on Python3. Or some people, who have been using old Linux distributions, might wish to upgrade their existing Python version. This article will guide you to install Python or upgrade the Python version in your Linux systems. Here we go!


Installing or Upgrading Python in Linux

First of all, we will see how Python can be installed on the Linux systems, if it is not already there. We do have plenty of package managers in different flavors of Linux distributions- apt-get and dpkg (for Ubuntu), yum (Yellowdog Update Manager, for CentOS/RHEL), zypper and yast (for SuSE Linux), to name a few. These package managers have made our life very easy, you just need to issue a command and they will search for the required packages and their dependencies, fetch them and install them for you. You need not download packages and their dependencies individually, which rather would have been a difficult task if there were no package managers.

I have a system with CentOS 7 installed in it. I don't have Python installed in it. So, I can install it using yum command as shown below:

# If you are 'root' user
$ yum install python

# If you are 'non-root' user
$ sudo yum install python

The command will not work for Ubuntu, as we have different package manager for that Linux distribution - apt-get, as mentioned earlier. So, for Ubuntu based systems, we can install Python using apt-get command as below:

$ sudo apt-get install python

This will install Python in your Linux system. We can check the current version of Python installed in the system with the command - python -V (capital letter 'V') or python --version.

$ python -V
Python 2.7.5

$ python --version
Python 2.7.5

Another way of installing Python is to download, build and install from source. This method can also be used to upgrade Python to a higher version. Let's say, we need to update the Python version from 2.7.5 to 3.5.2. For this, we need to download the source archive from the Python download page available at - https://www.python.org/ftp/python/.

$ wget https://www.python.org/ftp/python/3.5.2/Python-3.5.2.tgz

This file is an archive and needs to be extracted. This can be done using tar command as below-

$ tar -xvzf Python-3.5.2.tgz

It will be extracted to a directory - Python-3.5.2, which you can verify using ls command. In the next step, we would need to configure, build and install Python. For that, we need to change to the directory where our archive is extracted, using cd command. Then, we configure the installation directory with the command - ./configure --prefix=/usr/local. For this, you need to have a C compiler installed in your system. If it's not there, it will display an error message. You can issue yum install gcc command in order to install GNU C Compiler in CentOS (sudo apt-get install gcc in case of Ubuntu). Now, we need to install Python and we do this by using make altinstall command. Thus, we have used below commands to configure and install Python using the extracted archive-

$ cd Python-3.5.2
$ ./configure --prefix=/usr/local
$ make altinstall

It will take some moments for the installation to complete. When it is done, we can verify the Python versions installed by typing on terminal python[TAB][TAB]. It should show both the versions present in your system.

$ python
python    python2    python2.7    python3.5    python3.5m    python3.5m-config

$ python2.7 -V
Python 2.7.5

$ python3.5 -V
Python 3.5.2

Thus, we now have two versions of Python with us, it's up to us which one to use. With this, we also came to an end of this article. In the next article, we would be learning Python variables, constants and datatypes in the next article of this tutorial series. Please let us know about your views and opinions in the comment section below.

This article is originally published at www.codeninja.in - How to Install or Upgrade Python in Linux Systems

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