Create your first app on Linux using Python and Flask

Whether you play or work on Linux, this is a great opportunity for you to program in python. Back in college I wish they had taught me Python instead of Java, it was fun to learn and useful in practical applications like the yum package manager.

In this tutorial, I will take you to use python and a micro-framework called flask to build a simple application to display useful information such as the memory usage of each process and CPU percentage.

Prerequisites

Python basics, lists, classes, functions, and modules. HTML/CSS (basic).

You don’t have to be an advanced python developer to follow this tutorial

Installing Python 3 on Linux

Python is installed by default on most Linux distributions. The following command will let you see the installed version.

[root@linux-vps ~]# python -V
Python 2.7.5

We will use version 3.x to build our app. According to Python.org, improvements are only being made to this version now and are not backwards compatible with Python 2.

Note: Before starting, I strongly recommend you to try this tutorial in a virtual machine, because Python is a core component of many Linux distributions and any accidents may damage your system .

The following steps are based on Red Hat versions such as CentOS (6 and 7). Debian-based versions such as UbuntuMint and Resbian can skip this step. Pythonn 3 should be installed by default. If it is not installed, please use apt-get instead of yum to install the corresponding package below.

[leo@linux-vps] yum groupinstall 'Development Tools'
[leo@linux-vps] yum install -y zlib-dev openssl-devel sqlite-devel bzip2-devel
[leo@linux-vps] wget https://www.python.org/ftp/python/3.4.2/Python-3.4.2.tgz
[leo@linux-vps] tar -xvzf Python-3.4.2.tgz
[leo@linux-vps] cd Python-3.4.2
[leo@linux-vps] ./configure
[leo@linux-vps] make
# 推荐使用 make altinstall 以覆盖当前的 python 库
[leo@linux-vps]   make altinstall

After successful installation, you should be able to enter the Python3.4 shell using the following command.

[leo@linux-vps]# python3.4
Python 3.4.2 (default, Dec 12 2014, 08:01:15)
[GCC 4.8.2 20140120 (Red Hat 4.8.2-16)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> exit ()

Use pip to install packages

Python has its own package management, similar to yum and apt-get. You will need it to download, install and uninstall packages.

[leo@linux-vps] pip3.4 install "packagename"    
[leo@linux-vps] pip3.4 list
[leo@linux-vps] pip3.4 uninstall "packagename"

Python virtual environment

In Python, the virtual environment is a directory where the dependent environments of your project are placed. This is a good way to isolate projects with different dependencies. It allows you to install packages without sudo commands.

[leo@linux-vps] mkdir python3.4-flask
[leo@linux-vps] cd python3.4-flask 
[leo@linux-vps python3.4-flask] pyvenv-3.4 venv

To create a virtual environment you need to use the "pyvenv-3.4" command. The above command will create a directory named lib inside the venv folder, where the packages that the project depends on will be installed. A bin folder will also be created here to contain the pip and python executable files in this environment.

Activate a virtual environment for our Linux system information project

[leo@linux-vps python3.4-flask] source venv/bin/activate
 [leo@linux-vps python3.4-flask] which pip3.4
~/python3.4-flask/venv/bin/pip3.4
[leo@linux-vps python3.4-flask] which python3.4
~/python3.4-flask/venv/bin/python3.4

Install flask using pip

Let us continue to install the first module flask framework, which can handle access routing and Rendering displays our app’s template.

[leo@linux-vps python3.4-flask]pip3.4 install flask

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