What I learned from writing three Python books in a year
Over the past year or so, I have written three e-books on various topics in Python programming. Although I certainly don’t consider myself to be an expert on self-publishing, I have learned a bit in this time, so I will share it here. I hope you might find it useful.
This article covers four stages:
I have found the whole process takes me about 3 months, if I put most of my hobby time into it. …
Process images in 3 lines of Python
Pillow is a versatile and popular Python imaging library. The ImageEnhance module is a particularly useful module within Pillow. It can be used to adjust colour, contrast, brightness and sharpness in a few simple lines of code.
Each image enhance function is implemented as an object that implements the
_Enhance interface. The interface provides a single method:
For example, the
ImageEnhance.Brightness class controls the brightness of an image, It has an
enhance method that it inherits from
factor is a number that controls the effect. For example, for
factor of less than 1.0 makes the image darker (and a value of 0.0 makes the image completely black). A
factor of greater than 1.0 makes the image brighter. A
factor of exactly 1.0 …
Easy animation with generativepy
generativepy makes it very easy to create animated GIFs. This can be done with a simple script, and usually results in a fairly well optimised GIf file.
gif module makes use of the gifsicle application. This can be downloaded for free, and must be installed on your system in order for the
gif module to work.
GIF (Graphics Interchange Format) is a bitmap image format that was developed in the 1980s for transferring images over networks. …
Deriving new functions with functools
Functional programming is a paradigm in which functions form the fundamental building blocks.
It should be no surprise that functional programming includes several techniques for deriving new functions from existing functions. This is analogous to object oriented programming, where classes are the building block, and we have various ways to derive new classes from existing ones (inheritance and composition, for example). In both cases, the aim is the same — to reuse existing code (following the DRY principle, don’t repeat yourself).
Partial application is one such technique.
Here is a function that returns the value of
x, clamped to the range
b. That is, it returns the value of
x is less than
a (in which case
a is returned), or
x is greater than
b (in which case
It is, of course, vital to test software. There are various ways to test software, including:
Simple implementations of the List and Maybe monads.
In the article on the Failure monad we looked at a simple definition of what a monad is:
A monad is a design pattern that allows us to add a context to data values, and also allows us to easily compose existing functions so that they execute in a context aware manner.
In this article we will look at two other common monads:
A List monad allows us to process lists of values, without cluttering our code with looping constructs.
As with the Failure monad, our List monad should do three main…
A simple implementation of the Failure monad.
Image by Safijc
Monads have a reputation for being difficult to understand, but in this article we will look at a simple Python implementation of a simple monad. This will hopefully give some insight into what monads are all about.
In functional programming, we use functions as our primary building block, and function composition as one of the basic ways to structure our code. By function composition we mean functions that call other functions, like this:
y = str(neg(int(x)))
This composed function takes a string, converts it to an integer, negates it, and converts it back to a string. …
Converting individual markdown pages to html.
In a previous article we looked at what static sites are, and how they work.
Now we will look at how to convert a single markdown file into an HTML file.
This diagram from the previous article shows the basic process for converting a set of markdown files into the required HTML files for a complete website:
This time we will look in more detail at what is involved in converting a single page of markdown into the corresponding HTML file:
Here is an example markdown file, test.md:
author: Martin McBride
title: Features of markdown
List comprehensions are great at what they do. But maps are something rather different, and they have their place too.
A list comprehension is a clever little Python construct that can build a list from another list (or other iterable). For example:
k = [x + 3 for x in s]
This code takes an iterable
sand adds 3 to each element, returning the result as a list. So if
[1, 2, 3]the result would be
[4, 5, 6].
We could do this with a the map function:
k = list(map(lambda x: x + 3, s))
This is obviously longer and uglier than the list comprehension. That is hardly surprising because this example is exactly what list comprehensions are for. …
Static site generators, how and why to create your own.
Before looking at how to build a static website using Python, we will look at exactly what a static site is and what the advantages are.
And, since there are already a number of free static site generators, why would you want to write your own?
A static website simply consists of a collection of HTML files on a webserver. When you access a particular URL, the server just sends the file to your browser, as is, unchanged.
My site, PythonInformer.com is a static website. When you access this page: