Articles about Python

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Python is one of the most versatile programming languages in the world. With Python, you can control electronics, build web applications and perform machine learning.

In this page, you can find articles on Python references, coding and application setup.

How to host your Python 3 Flask MVP with Supervisor on Ubuntu Server 16.04

Due to its minimalistic design, the Python Flask framework is ideal for building the web server layer of minimal viable products (MVP) to validate customers’ needs. However, development work is just one part of the user validation efforts. To ensure that our customer can access our Flask MVP and provide feedback as and when they are available, we will need to get it running with as a server daemon.

Supervisor is a convenient tool for running applications as a server daemon.

This post documents the steps that I took to host a Python 3 Flask MVP with Supervisor on an Ubuntu Server 16.04 instance.

How to setup Ubuntu Classic Server 16.04 on Raspberry Pi 3 for running Python 3 applications

Most of the customers who wanted to try out my minimal viable products (MVP) would provide me with an instance of Ubuntu Classic Server 16.0x these days. As such, it makes sense for me to trial my MVPs on the Ubuntu Classic Server 16.0x to ensure that I spend minimal time in deploying my MVPs to validate my customers’ needs. Since I have a few Raspberry Pi 3s lying around in the house, I can install a version of Ubuntu Classic Server 16.0x to serve as the development server for me to trial my MVPs.

Fortunately, the good folks at ubuntu-pi-flavour-maker.org had put up an optimised Ubuntu Classic Server 16.04 image for Raspberry Pi 3.

This post documents the steps that I took to run Ubuntu Classic Server 16.04 on my Raspberry Pi 3 for running Python 3 applications.

How to serve static files with Python 3 + Flask

Python Flask is a good microframework for building a minimal viable product to validate our ideas on the Internet. A modern web application encompasses documents that tell the web browser how to build the visuals of our web application and communicate with our server backend. Such documents are usually static in nature and are served as they are to the web browser without any processing from the server end.

Comparing setting up an instance of the Nginx server with adding code in our Flask application, the latter can be a more convenient way for us to realise our minimal viable product. This post documents the proof of concept that I did to serve static files with Python 3 and Flask.

A platform independent way to set your Python Path for your Python applications

In a software development house where desktop computers run Microsoft Windows while servers run Linux, software developers will have to ensure that the Python code that they wrote on their Windows machine can run on the deployment servers which are running Linux.

One unavoidable task for Python application developers is the importing of functionalities that are contained in other Python scripts. In order for the Python interpreter to find the Python scripts that are referenced by Python import statements, the Python Path will need to contain the URLs of the directories that contain the Python scripts to be imported.

How to sort a python dictionary by keys

I am a fan of hash tables when I need to implement logic that augments computation results to a common data structure that need to be used across several function bodies. The ability of the hash table in providing constant access by key helps me in keeping my logic from taking too much time to complete.

Python’s version of hash tables are known as a dictionaries or associative arrays. Apart from augmenting computation results to values of my Python dictionaries, one common task that I often perform is sorting the results by the dictionary keys. In this post, I document how I can sort my Python dictionary by its keys.

How to generate n-grams in Python without using any external libraries

There are many text analysis applications that utilize n-grams as a basis for building prediction models. The term “n-grams” refers to individual or group of words that appear consecutively in text documents.

In this post, I document the Python codes that I typically use to generate n-grams without depending on external python libraries.

Ensuring that your Supervisor subprocesses can run your Python applications properly behind your http proxy on Ubuntu Server 14.0.4

I had been using Supervisor to run my Python application for quite a while on a Ubuntu Server 14.0.4 box.

There was this OAuth feature that I had implemented on my Python Flask application to allow my users to sign in with their social account.

After completing the OAuth feature and ensuring that it worked fine on my development environment, I deployed the feature on my Ubuntu Server 14.0.4 instance.

However, my Python application encountered a HTTP request timeout error when it attempted to contact the OAuth server to authenticate my user login.

It turned out that there was no HTTP and HTTPS proxy settings available for my Python application to use when it tried to contact the OAuth server which is sitting somewhere in the Internet.

This post documents three ways which I had considered for propagating HTTP and HTTPS proxy settings to my Python application via the http_proxy and https_proxy environment variables.

Supervisor configurations to ensure that my Python Flask application releases binded port(s) during a supervisor restart

We use Supervisor to help keep our Python based applications running. One of our applications was built on the Python Flask framework to provide a RESTful api to connecting clients.

With continuous integration in place, we need to restart all our Supervisor managed applications whenever there is a change being merged to the master branch in our Git repository.

This post documents the Supervisor configurations to ensure that my Python Flask application releases any port that it had binded to when Jenkins send the command to restart the Supervisor and the processes that it manages.