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Articles about programming

  1. Command-line versus GUI program

    TL;DR

    When you are exploring a problem, in general first write a command-line program whenever possible.

    It will take less effort to write then a full-blown GUI.

    Introduction

    Recently I wrote a program to remove the protection from ms-excel files.

    The original version was written as a command-line program. Later I re-used the relevant code for a GUI program for use on ms-windows. This was mainly for the benefit of some colleagues who are not comfortable with using the command-line.

    In this article I want to contrast the two programs.

  2. How convenient is multithreading compared to multiprocessing?

    There are basically two ways in which one can make use of a modern CPU with multiple cores for computationally intensive work.

    1. Using multiple threads within one program (multithreading).
    2. Using multiple (single-threaded) programs that communicate (multiprocessing).

    In the first case, all data is implicitly shared. In the second case, data must be explicitly shared or communicated.

    The first option is often said to be more convenient. I would like to make the case that this usually makes the task more difficult, because of the need to manage all shared data.

  3. Including binary data in Python scripts

    Sometimes I need to use some binary data (e.g. a bitmap image) in a Python script. In a package, you can store this data portable in a data subdirectory of a modules using the package_data argument of setuptools.setup. This won’t work in a standalone script. You can of course make your script into a package, but here I want to show an alternative solution.

  4. ImageMagick: convert vs Wand

    The ImageMagick suite has been in my software toolbox for years. It is my go-to tool for manipulating bitmap images. Over the years I have written several front-ends for specific tasks for in Python.

    In general, I have used the subprocess module to launch convert or mogrify from Python.

    With the release of Wand 0.5.0 which supports ImageMagick 7, I decided to try that by porting one of my scripts (foto4lb) to it. This turned out to be slower than using convert directly.

    But now it is 2021. Py-wand is at 0.6.7 and it is time to try again.

  6. Database scheme for resin recipes

    This document explores how an SQLite database could be used to store data for the resin-calculator. Normally, the recipes are a dictionary keyed to the name of the resin. The value of each recipe is a list of (component, parts-by-weight) tuples. Since a database only contains tables, where each row has the same form, how do we store such infomation in a database?

  7. Doing calculations with Python

    As an engineer I do a lot of calculations. These can be done with pen and paper and a calculator, in an IPython notebook or in a throwaway spreadsheet. All of these methods have shortcomings, though.

    Pen and paper is hard to share and (in my case) hard for others to read. In IPython you can assign the results of calculations to a variable, but you have to perform a separate action to display them. And spreadsheets in general show you the results but not the calculations.

    So I wrote a simple function in Python to help me with that. Using this function I can print both simple assignments and relatively complex calculations. And it shows both the calculation and the result.

  9. Structures in Python

    Sometimes I miss the C’s plain old struct in Python.

    Of course Python has dictionaries, but I prefer to write a.b over a['b'].

    Here are several ways of doing something akin to a struct in Python.


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