Faster Image Transforms With Cython

Python to Cython

This is the second post on how to accelerate Python with Cython. The previous post used Cython to declare static C data types in Python, to speed up the runtime of a prime number generator. In this post we shall be modifying a more complex program, one that performs an image transform on a map. This will allow me to demonstrate some more advanced Cython techniques, such as importing C functions from the C math library, using memory views of Numpy arrays and turning off the Python global interpreter lock (GIL).

As with the previous post, we shall be making a series of Cython modifications to Python code, noting the speed improvement with each step. As we go, we’ll be using the Cython compiler’s annotation feature to see which lines are converted into C at each stage, and which lines are still using Python objects and functions. And as we tune the code to run at increasingly higher speeds, we shall be profiling it to see what’s still holding us up, and where to refocus our attention.

Although I will be using Python 3 on a Mac, the instructions I give will mostly be platform agnostic:  I will assume you have installed Cython on your system (on Windows, Linux or OS/X) and have followed and understood the installation and testing steps in my previous post. This will be essential if you are to follow the steps I outline below. As stated in the previous post, Cython is not for Python beginners.

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From Python To Cython

This longer post will show you some of the coding skills you’ll need for turning your existing Python code into the Python-C hybrid we call Cython. In doing so, we’ll be digging into some C static data types, to see how much faster Python code will run, and restructuring some Python code along the way for maximum speed.

With Cython, all the benefits of Python are still yours – easily readable code, fast development cycles, powerful high level commands, maintainability, a suite of web development frameworks, a huge standard library for data science, machine learning, imaging, databases and security, plus easy manipulation of files, documents and strings. You should still use Python for all these things – these are what Python does best. But you should also consider combining them with Cython to speed up the computationally intensive Python functions that needs to be fast. Continue reading “From Python To Cython”

The Toolkit – Updated

SpannersAlas, dear Windows, it was not to be. I’m afraid I’ve been seeing other platforms. Specifically, I’ve been spending time with OS/X behind your back.  It was just too painful to be with you.  All those arguments, the shouting, the hair-pulling, the throwing things across the room.

Sure, you’re a lot less volatile than you used to be. And you don’t do the tearful breakdown thing any more. Yes, I know I can do almost anything with you that I can with OS/X, but everything just takes longer. OK, you want me to be honest? Fine. I find you excruciatingly frustrating to be with.  Why is it always ME navigating around YOUR moods? I mean, why is it that after 25 years, everything with you is STILL a workaround?

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GUI Template For Python: Part 2

This is the second of two posts on how to quickly create a Tkinter dashboard for your command line Python programs. The Tkinter widgets and programming techniques it introduces are a sequel to the previous post.

So far, you have an interactive graphical way of opening a file to analyse it in some way with your own logic, entering text to use as triggers or search strings, setting your own program flags on/off using check boxes, switching between two or more mutually exclusive program flags using radio boxes, controlling access to widgets and the variables they control, calling your own logic, and saving your results in a new file.

This post will build on these skills by showing how to create a dashboard to accept numerical input, perform different kinds of type- and value-checking, and select multiple input files simultaneously using a Tkinter GUI file selector. The solution will be multi-platform, and is shown running above on (from left) Windows 10, Mac OS/X and Linux Mint above. This post will explain how to create the same thing for your own program. Before proceeding, make sure you’ve read and understood the previous post.

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GUI Template For Python: Part 1

The next problem I needed to solve was to come up with a simple graphical user interface (GUI) template as a front-end for configuring and launching any Python code or module I may wish to write or run. Initial impetus: I didn’t want to have to write a user interface from scratch every time I wrote some Python code to manipulate text, data or files. Bonus reason: if I made the GUI template generic enough, others might be able to use it to create their own user interfaces.

This would solve a problem that occurs in many technical fields. A university professor may have a post-doc researcher on her team, one who has written a complex command line program performing, e.g. image processing, AI or genetic analysis. At some stage, there may be some highly repetitive tests that can be performed by someone less technical, freeing up the researcher. She wouldn’t want him running these repetitive command-line tests with code only he knows how to run or, worse, sitting around designing complex user interfaces for others to use it. It would be better to get an intern or research assistant (or even a temp) to run the tests using a GUI that the researcher can knock up in a day or two. This would free him up to concentrate on his research. And finish it faster. Continue reading “GUI Template For Python: Part 1”

Analysis Tool For Literary Texts

The first problem I wanted to solve was to write a short program that would allow me to perform basic textual analysis of any work of literature.

I wanted to be able to study the richness of different authors’ language by looking at how they used neologisms (their own made up words), pseudo-archaisms, invented their own contractions for authentic speech, or used hyphenated compound words, etc. I also wanted to be able to list all the characters and place names (proper nouns) mentioned in a text.

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The Toolkit

SpannersOK, first things first. What tools will I be using?

After talking to a good friend who is an experienced coder, I decided on the following:

The IDE

Spyder, running Python 3. It seems to have everything I need, including a good debugger, a variable explorer, hot-linking to function definitions, auto-completion typing, Matplotlib, QT, plus a choice of either a Python and iPython console (each with their different strengths). The bundle I went with is Spyder for WinPython-64bit (WinPython-64bit-3.4.4.3Qt5). The QT will be useful later.

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