Tuesday, 9 August 2011

Python and Tkinter: wonderful

Having time on my hands at the moment, and no work commitments - that's another story though - I decided to start taking a new look at the robotics stuff I was playing with a year or so ago.

I'd written nearly all of the code to make a six-legged robot - a hexapod - walk with various different gaits and postures - the so-called inverse kinematics. It was in straight C, since I intended it run on a little embedded CPU which had no support for C++, nor floating point for that matter. And I'd built a development environment, including visualisation for the leg movements, using Visual Studio.

Things have moved on since then, though. For one thing I've pretty much switched to Linux for my computing environment. For another, the Roboard has really become the obvious onboard computer - it is now available with Linux, and it offers a full-function x86 including floating point, in a tiny size that will fit in my fairly small hexapod. And since it supports full GCC, I can write the code in C++. The C code is just so cluttered - I can't for the life of me imagine why anyone would prefer to code in C. It's full of irrelevant details that make it hard to read and even harder to get it to work. So, a rewrite is called for.

The only problem, is the GUI that I'd painfully created using the Visual Studio tools. Painful because there are 6 legs, and each has numerous parameters and state variables. I'd created the dialog box from hell. Every tiny change meant nudging numerous components around to get it to look right. What a pain. But it was done, for now anyway.

That was when I thought about Tkinter, which I've never used before. I've become a huge fan of Python in the last couple of years, using it for anything where performance is not a big deal. I also wrote a very powerful Python-based scripting system for my now-defunct employer, using Boost Python. So using Python and Tkinter for the GUI was kind of an obvious thing to do.

Somewhere in the mists of history I acquired Python and Tkinter Programming, which I think is the definitive book on the topic. I skimmed that, and with frequent help from Google - especially this site - started putting my new GUI together.

What a pleasure! Tkinter automatically takes care of making a reasonable layout, given some general guidance through the pack and grid functions. You no longer have to think about the minutiae of positioning, or spend ages getting boxes to line up with each other. I just couldn't help putting together a bit of infrastructure for collections of config variables, so they are now super-easy - just a list of names and default values and Python and Tkinter take care of everything.

In total it has probably taken me about 6 hours to get everything together - but that included learning Tkinter from scratch and writing quite a bit of infrastructure. And now I have everything I need to control my inverse kinematics, and have an animated visualisation of what it's doing.

I'll never do GUIs any other way now. Tkinter is wonderful!

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