Older articles (2/16)

1. 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.

2. 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.

3. 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.

4. State machines in Python

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

5. 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

6. 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 …

7. 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.

8. Removing big files from git history

   By accident I checked 60-odd full-size photographs into the git history of my website. I shrunk them in a next commit, but the history was still there leading to a bloated .git directory. This took a lot of time when making backups. This documents how I cleaned up this mess.

9. Using gnuplot from Python

   According to my revision control systems (rcs in those days), I’ve been using gnuplot to make graphs since at least 2002. And I’ve got it set up via a custom gnuplotrc to match the style of the TeX documents I often use the graphs in.

   At work we have an Instron 3369 machine for material testing. Recently, I wanted to visualize some tensile test data in ways that I couldn’t get into the test report.

10. Comparing stock ffmpeg with optimized ffmpeg

    Recently FreeBSD changed the multimedia/ffmpeg port to drop the -ffast-math and -fno-finite-math-only from the CFLAGS when building an optimized binary. The following experiment was conducted to see how much of a difference this makes.