Older articles (2/16)

1. Using sqlite3 for time management

   After some initial experiments with sqlite as a replacement for a json data file format (which I did not pursue in the end), I have now started using sqlite in earnest. And I must say that I quite like it.

2. 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?

3. Convert RCS history to git

   Before the rise of git, I used rcs as my version control system. Because I want to standardize on git, I am slowly converting old repositories.

   In this article I’ll be converting my old perl scripts in ~/src/perl.

4. 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.

5. Improving my Python coding

   With leading white space governing the indentation level and so the grouping of statements, Python code already looks relatively clean.

   Yet there are additional tools that will help you improve your code.

6. 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.

7. State machines in Python

   State machines can be relatively easy defined as a data structure.

8. Fixing dependencies after mesa ports consolidation

   After the 2017-05-12 mesa port consolidation, there were packages left with missing dependencies. This is how to fix them

9. Building gphoto2-ffi on FreeBSD

   Download

   Clone the repository from https://github.com/jbaiter/gphoto2-cffi.

   > cd ~/github
   > git clone https://github.com/jbaiter/gphoto2-cffi
   

   Build

   I had to specify where to find the include files.

   > env C_INCLUDE_PATH=/usr/local/include python3 setup.py build
   

   Install and clean-up

   # python3 setup.py install
   # python3 setup.py clean …

10. Evaluating Zstandard compression

    Recently I became aware of the zstd compression program. I wanted to see how it stacks up against gzip, bzip2 and xz.

    TL;DR

    Compression with zstd is blisteringly fast.

    But xz still yields the smallest files.