Archive for Dojo

NetworkZero at the London Python Dojo

The London Python Dojo was hosted yesterday by Hired, an unashamedly promotional move by the job search marketplace firm. Their offices are in Southwark, not far from Borough or London Bridge, a welcome change from the Old Street area where we’re often hosted.

After the usual beer & pizza, kindly provided by our hosts, we had a fairly quick round of voting which ended up with most people wanting to try out my Network Zero package, advertised and just pipped to the post at the previous Dojo. I gave a quick demo and explanation, pointed to the github repo and the readthedocs page and let people loose.

Amusingly, our hosts — not being a tech startup which most of our hosts are — didn’t really have an easy way for guests to access WiFi. They did offer us an ethernet cable. So, in a network-centred Dojo, we had a combination of link-local connections, tethered phones, and a wired internet connection shared via a OS/X hotspot. Apart from anything else, it really showed up some of the shortcomings of the NetworkZero approach, especially in the area of the UDP broadcasts supporting the advertise/discover mechanism.

Fortunately, everyone got something working after a bit of experimentation and several people provided PRs, raised issues, or just told me of difficulties they were having. Thanks especially to Sandy for bringing his undoubted networking expertise to bear on the innards of the project.

I had held off uploading anything to PyPI until after this event in case any obvious instability or major flaw were to show up. But this caused some surprise when people couldn’t simply pip install networkzero. (Fortunately it’s very easy to clone the repo and pip install -e .). I’ll be reviewing the issues & PRs and then, hopefully, publishing to PyPI.

I now want to put the code in front of teachers to get their feedback on its usefulness and usability.

Thanks, of course, to our hosts — Hired — and to O’Reilly who continue to support us with a book to give away at the end of the Dojo.

ESP8266 Dojo at Marks & Spencer Digital

I don’t usually reference chip names in my post titles, but this neat little chip was very much at the heart of yesterday’s London Python Dojo at Marks & Spencer Digital near Paddington.

For those who don’t know, Damien George, creator of MicroPython recently launched a Kickstarter to help development of MicroPython, specifically targetting the ESP8266. He was good enough to bring along a handful of boards with this chipset with a view to our hacking on them with Micropython. He explained to us something of the background of MicroPython (which is now his full-time job, hence the Kickstarter) and of the chip which seems to have a hit a sweetspot of power and price and is hugely popular among hobbyists far removed from its origins in a Chinese technology factory.

To honour Gautier’s turn as cat-herder, we’d been having a bit of Franglais badinage on the organisers’ mailing list. But then Nicholas, who’d arranged for us to use M&S, went one step further and our pre-meetup refreshments took the shape of wine, cheese & baguettes. (And some suitably French musique!).

Inevitably, when it came down to getting up-and-running in our different teams, there was a fair scramble as most people had to come up from scratch to getting a board flashed and then working with some kind of peripheral. Damien had helpfully set things up so a simple “import mswifi” would attach to the necessary WiFi, but after that we were on our own. We had two small teams with only one board but we did have a neopixel strip, so we set to doing something with that.

One stumbling block was that all of Damien’s demonstrations (via Serial-over-USB) had been on a Linux box and we had a mixture of Linux, Mac & Windows. There was an amount of faffing about to recognise and connect to the device on various boxes, but we ended up using a Linux box which led us to the next problem: everything has to happen in the interactive REPL, short of a complete reflash. So Tom was shuttling text to and from an editor and the embedded REPL via picocom. All this is happening quite quickly, and with little or no documentation on the (quite extensive) facilities which MicroPython brings on the device. So you become both pragmatic and inventive in your workarounds.

Finally we got a simple example where a Heroku-based Flask app allowed someone to set up an array of RGB colour values while the ESP8266 device would poll that website periodically, decode the JSON, and change the pixel array accordingly. It was rough and ready, but it worked.

Other teams did similar-ish things: one was trying to use an add-on screen to render the well-known Star Wars ASCII Art telnet feed. Another team had a small fan controlled by the device and managed, like ours, by a text file on a web server which was updated by Carles via an SSH session on his phone!

A number of us had ordered devices (at short notice) for the event, but most hadn’t received them in time not least because the same distributors are currently flooded with orders for the brand new Raspberry Pi 3. Hopefully, when they do arrive we’ll be able to get MicroPython working on them without difficulty.

You can see a few photos via our Twitter feed.

Thanks again to M&S Digital and Nicholas for hosting and for the French food, for O’Reilly for continuing to supply us with books as giveaways, and to Gautier for keeping everything on an even keel. And especial thanks to Carles who stuck with me when I thought I’d lost my Oyster card.

See you next month.

Coding with youngsters using pgzero on RPi: Part I

An eager young coder on Step 3

Some of you will know that several-times pyweek winner Daniel Pope has put together a simple framework called pgzero to sit on top of pygame. It’s Python 3 only and is especially aimed at educational use, and we spent the last London Python Dojo coming up with examples which used it.

Its main selling point is that it supplies behind the scenes some of the boilerplate code you’d otherwise have to write to get pygame up and running in a game loop. The simplest valid pgzero game is an empty .py file! From this, pgzero will produce a blank window of the default size, which will exit if you press Ctrl-Q. Adding a few “magic” constants will get you a window of a certain width & height, with a title and its own icon. After that, just define draw() and update() and add on_<event> handlers. And you have the makings of a game. There’s a built-in Actor class which essentially acts as a sprite, and easy-to-use image & sound loading. Plus some other goodies we didn’t use.

My team was responsible for the Breakout clone at the Dojo and I took it away and demonstrated it at the next evening’s Twickenham Coding evening, a friendly meetup in a room over a pub attended by teachers, code club leaders and educators. Altho’ we’d developed on my Windows laptop, I’d already planned to use the Raspberry Pi, about which more later, and I was very pleased when it ran on the Pi without a glitch at the Twickenham meetup. The message from the teachers I showed it to (mostly at the upper-Primary range) was: still too much code. But I got some useful feedback and set to work to adapt it.

My plan was to use pgzero and the Breakout game as the basis for a short series of workshops at the boys’ club I help to run in west London. But the lads aren’t into coding as such, and I knew from past experience that they could easily lose heart and get distracted if they didn’t instantaneously produce a Call of Duty lookalike. So I aimed for two things: cutting down the code complexity so there were as few concepts as possible to get across; and breaking it up into chunks which I could present one at a time, each building on the code from the previous chunk.

The result, for the impatient, is in the piece-by-piece branch. But first, there are some yaks we need to shave.

The setup

Hardware

I was keen to use the Raspberry Pi for this.

  1. It’s cheap and so the club can afford to buy several of them; and one or two of the lads have their own
  2. It’s quite different from the (often literally) black box computers they’ll generally use so they don’t immediately see it as a mere entertainment source (ie they’re more likely to enter into a spirit of producing rather than only consuming)
  3. In later sessions I hope to introduce some simple electronics via the CamJam EduKit and similar things where the RPi excels
  4. It’s a Raspberry Pi! Everyone’s talking about them. Parents are keen on them. It creates a buzz around the activity which would be lacking if I’d used some other, equally capable, platform

We already had one RPi, an original Model B; someone tweeted that RS had Model B+ going at £16 each which is well within the budget I’d set for a couple more. Fortunately we have a number of monitors (VGA), which would otherwise have been beyond us to buy. The excellent PiHut also had the necessary accoutrements at affordable prices.

As everything was taking place in our club building, which isn’t networked, I used a spare laptop setup with lubuntu to run dnsmasq for a very easy local DHCP / DNS solution. The Pis were all wired to a simple 10/100 switch.

Expecting about 6 people, I’d planned to run in a classroom mode, with my laptop able to view individual screens if anyone needed help. I’d also thought of having my screen “broadcast” to theirs. I was a little surprised that there doesn’t seem to be a definitive way of doing this. iTalc2 looked promising, but needed a fair bit of setup. There are several commercial solutions, so presumably schools are able to budget for this kind of thing. In the end, I installed x11vnc on each of the RPis. But with only 4 boys in the end, and another tech-savvy leader, it was more sensible to physically wander around to help. I do plan to look into the reverse: broadcasting my screen. We don’t have any kind of projector at the moment, and in any case I’ve never found that a satisfactory solution for showing code.

The Software

The focus of the first sessions was the use of pgzero to produce the simple Breakout clone mentioned above. But first I had to bring the complexity of the code right down, taking advantage of the fact that pgzero hides away some of the messier boilerplate. These were first-time programmers and I would be throwing a lot of new concepts at them in a fairly short space of time. (Fortunately they’re all in Years 8 to 10 at school so I didn’t have to explain too much about coordinate systems and vectors).

Responding to an issue on the pgzero tracker, I’ve submitted a PR for a pure Python implementation of the pygame Rect class. The ostensible need was to allow for floating-point size and position changes. But a secondary effect, of more immediate use to me, was the possibility of adding arbitrary attributes to a Rect instance, such as colour and direction.

So the boys were working off my fork of the pgzero repo, installed via “pip install -e .” to track the development version. They were also unwittingly working off the piece-by-piece branch of my fork of the breakout code, although I was feeding it to them a piece at a time. I’d made use of the pgzero Rect to be able to add colour and direction as attributes, which did away with the awkward global variables of the original codebase. The result, though I say it myself, is about as stripped back as you can get while still actually doing something. The global blocks setup is a little clumsy, but the alternatives I tried were no better.

The Workshop

I’d set up our own Raspberry Pis and for the one lad who brought his own I did the necessary config while they were playing football outside. I persauded them all to close down Minecraft (”Look! It’s got Minecraft!”) and Mathematica (it’s got a shiny red icon, just asking to be pressed…).

I got them all to open a terminal window and cd to ~/work/breakout where I’d cloned and then started a new branch with no files. They ran IDLE3 and started a new file called “breakout.py” (or “Breakout.py” or “bereakout.py” depending on the skill of the typist). I got them to run pgzrun against their new file and use Ctrl-Q to exit the resulting window. So far, so good.

From this point on, I fed them one step at a time on paper from the piece-by-piece branch. I’d considered other options: projecting the code, having them “git checkout” to the right tag, even reading it out or live-coding it myself. But this seemed the most trouble-free option and, basically, it worked.

After they’d got each update working, I highlighted a few new or repeated features. (”That’s a name; you defined that earlier”, “That’s a function; you run all that code in one go by using the function name”) etc. One of our other club leaders, Albert, is also a professional coder (PHP) and was very able to help so between us we kept the pace going despite the variations in typing ability.

At the end of the first session they’d reached step 6 out of 12.

Takeaways

What worked?

  • The pacing was basically about right. One of the steps had a little too much code in it, but I needed to have a change of some sort at the end of each step, and there really wasn’t anything I could do about it
  • I was very pleased the way in which the boys worked out the obvious typing bugs; they very quickly spotted when uppercase/lowercase was wrong or when they’d misspelt a name. I very rarely had to point out anything obvious.
  • Step 4 (when the bat responds to the on-mouse-move event) was the winner. Simple as it was, the boys loved the interaction. When someone got it slightly wrong (bat.centrex = y) causing the bat to move horizontally as the mouse moved vertically, they all wanted to try it. When I suggested they swap both coordinates (bat.centrey = x; bat.centrex =y) they’d have stayed there for ages.
  • I encouraged them to change things (the screen size, the colours etc.) and I was pleased that one lad, after I’d explained how names work, changed his “bat” and “ball” names to something else — altho’ this caused problems later when I was helping him debug as I couldn’t tell which object was which!
  • Although I’d had planned for a two-hour session, the 90 minutes we ended up with was about right

What didn’t work?

  • I should have brought step 4 in a little earlier, perhaps creating the bat before the ball and then letting it move
  • Several times I had to draw things up on the whiteboard to illustrate the coordinate system etc. This probably would have worked better with a screen broadcast from an IDLE session.
  • I had intended to have them try things out in IDLE, starting from a “from pgzero.builtins import *”. This didn’t really happen, although I did get them to do some experiments with the modulo operator when explaining the colour looping for the blocks.

Conclusion

Overall, I was very happy with the way it worked. I had four non-programmers dive in and basically enjoy themselves. I’m hoping to use the next session to finish the game and get them to play around with bells-and-whistles (make it go faster, have a bat on each side-wall etc.). After that I hope to connect up some simple LED / buzzers to react to the game.

FWIW I’d love to do a networked version where the ball disappears off one screen and appears on the next. Each person’s ball could be colour-coded and a ball will only destroy blocks of its own colour, so you have to use balls from your neighbour’s games to finish your own. Or something. I love the idea of the social aspect that would introduce, as well as the fact that someone could have two or even more balls in play on their own screen.

Raspberry Pi-themed Dojo at BAML

Yesterday Bank of America once again hosted the London Python Code Dojo, this time at their St Paul’s offices. I don’t know what the normal use is for the room we were in, but it felt like a cross between a banqueting hall and something from Khazad-dûm. Very grand and with nice AV facilities: one big screen, several smaller screens and microphones. As is customary, the hosts provided beer & pizza, but as usual with BAML, in a somewhat classier mode, with slices and plates and a variety of drinks served by staff. All very much appreciated.

They’d also done all the setup, so we had 8 or 10 Raspberry Pi rigs with screens and enough keyboards and so on to go round. The networking took some doing and ended up being a cat’s cradle of very long ethernet cables all routing — I understand — through one all-the-data-you-can-eat phone connection! Which worked fine.

Al Broomhead and Tina Zhang gave a joint lightning talk on a couple of projects they’d been involved in on a recent Hack Day. Ben Nuttall from the Raspberry Pi Foundation had been good enough to come and join us and gave an overview of some of the resources they already have to help people use the RPi and to encourage any contributions the evening might bring forth.

Slightly differently from our usual approach, we had several different projects going during the evening. The idea was to come up with something which showcased the Raspberry Pi in some way. In the end, we had: a very simple approach to a door-challenge mechanism; a on-screen 7-segment display; an automated light which reacted to the hue of a chosen image; a text-adventure interface to Minecraft (”go forward; dig 5″); a morse-code reader using a Pibrella; and a couple of things which I’ve forgotten (sorry; someone ping me a reminder…).

At the end, of course, we had a name-draw for the book donated as usual by O’Reilly. And thanks go to BAML for their continued sponsorship of the Dojo. And to the BAML guys (and I think it was all guys) in particular for all the prep and tidy-up work to get the kit in place for us.

It was nice to see new people as well as the familiar faces. If anyone who was there wants to contribute their code or ideas to the Raspberry Pi Foundation, get in touch with Ben Nuttall. You can see a few photos via the @ldnpydojo twitter account. If any more show up we’ll try to retweet them.

London Python Dojo December 2014

I feel like a sub-editor just struggling really hard to avoid punny headlines like “A Unique Experience” and “5 Unique Solutions” and so on… because last night’s challenge was to recreate the Unix “uniq” command in Python. In fact, this was chosen only after a tie in the first round of voting giving us a top 4 rather than a top 3 and a triple-tie for second place in the second round, although with one clear winner. (Otherwise I was going to have to move onto a Single Transferrable Vote round).

It was nice to see quite a few new faces, 6 or so first-timers and several who haven’t been for a while or who have been only once or twice. Plus, of course, the old familiar faces. Fry IT continue to host us generously, including ordering artisan pizzas with enormous slices. And O’Reilly came across as always with a book for the giveaway at the end.

Most teams went for a fairly straight solution, one of them managing to carry a TDD approach pretty much throughout. One team had grander ambitions for field selection and datatype conversion, but their solution ended up on two different machines with not enough time to merge properly. I was a little surprised that no-one used itertools groupby, which is pretty much advertised as a drop-in for uniq.

You can see a few photos retweeted at the @ldnpydojo account. Back again in January, probably on the second Thursday. But watch the python-uk mailing list and @ldnpydojo for announcements.