Notes on everything: Install Python

This post is one of a series

Create an environment for Web development

Vagrant/Virtualbox
Install Apache or Nginx for PHP or Nginx for Python
Install MySQL / Install MariaDB
Install PHP / Install Python - You are here

Install Python3.6

We will install Python 3.6. At first, we will check what is installed and what is not:

$ yum list python*

Seems like Python 2.7 is installed in Cent OS 7 by default. But there is not Python 3.6 in this list. Seems like Python 3.5 is not installed in this OS by default. Do the following command to make a repository available to install Python 3.6:

$ sudo yum install -y https://centos7.iuscommunity.org/ius-release.rpm

This enables the repository of IUS Community Project. To install Python 3.6 from this repository, do this command:

$ sudo yum install -y python36u python36u-libs python36u-devel python36u-pip python-pip

To check if Python 3.6 is successfully installed, do the following command:

$ sudo python3.6 -V 
$ sudo which python3.6

If the version is displayed, it is success.

Re-start your Apache (httpd) after the installation.

$ sudo systemctl restart httpd

FYI commands for CentOS6

$ sudo yum install -y https://centos6.iuscommunity.org/ius-release.rpm
$ sudo yum install -y python36u python36u-libs python36u-devel python36u-pip python-pip
$ sudo locate python3.6
$ sudo service httpd restart

Versions of Python

But even if you install python 3.x, the python called by "python" command on the console is usually python2.7. You can check it by running this command:

$ python -V

This is because python2.7 is sometimes used by system. Don't change the "python" symlink.

To use python3.6, run commands like this:

$ python3.6 -V

pip for Python2.7:

$ pip

pip for python3.6:

$ pip3.6

Hello World with Python

We will create a "index.py" file to display "<H1>This is my first CGI script</H1> Hello, world!" in a browser. Create a file named as "index.py" at C:\MyVM\MyCentOs. (I mean, inside the share folder of Vagrant). Inside index.py, write as follows:

#!/usr/bin/env python
# -- coding: UTF-8 --

print("Content-Type: text/html\n\r")
print ("""
    <TITLE>CGI script ! Python</TITLE>
    <H1>This is my first CGI script</H1>
    Hello, world!
""")

Please note that the line break type must be LF, not CR/RF. Python doesn't work without linebreaks because of its syntax. Use Visual studio code to see what linebreaks are used in the file.

Now do the following command to change the apache's config file:

$ sudo vi /etc/httpd/conf/httpd.conf

To change the text, hit "a" on your keyboard then insert mode will start.

Press a on your keyboard to be insert mode and you can edit the file. Press escape key to stop the insert mode. After stopping the insert mode, press Shift + g to go to the lowest row. :wq or Shift + zz to save and close the file. You can go to command mode by pressing : on your keyboard. To exit the file without saving the file, inout :q! and enter. To search a word, press ? then write a word what you want to search. For example, if you write ?aaa and press enter, "aaa" is searched and highlighted in the file. Press n to jump to next match.)

Add "ExecCGI" in the lines of "/var/www/html" as follows:

<Directory "/var/www/html">
Options Indexes FollowSymlinks ExecCGI
AllowOverride None
Require all granted
</Directory>

And add .py to Add handler:
AddHandler cgi-script .cgi .py