Mailman 3 July 2012 - Edu-sig

a short essay about programming
by kirby urner Dec. 8, 2022

Dec. 8, 2022

A common "error" (not too serious) that I see in beginning Python (and no doubt other languages, but Python is the one I'm teaching), is having a while condition that appears to put a lid on things, but then the flow all leaks away through break statements, such that the "front door" condition is never revisited. while guess != secret: guess = int(input("Guess?: ") if guess == secret: print("You guessed it!") break else: print("Nope, try again...") What's messed up about the above code is you never really go back to the top in the case where you'd get to leave. Rather, you exit by the back door, through break. So in that case, wouldn't have been simpler and more elegant, even more "correct" (dare I say it) to have gone: while True: # no ifs ands or buts guess = int(input("Guess?: ") if guess == secret: print("You guessed it!") break else: print("Nope, try again...") I see lots of heads nodding, and that could be the end of the matter, but then a next question arises: wouldn't this also be a more correct solution?: while guess != secret: guess = int(input("Guess?: ") if guess == secret: print("You guessed it!") continue # instead of break else: print("Nope, try again...") We're back to having a variable while condition, not a boolean constant, but this time we actually exit by means of it, thanks to continue or... while guess != secret: guess = int(input("Guess?: ") if guess == secret: print("You guessed it!") else: print("Nope, try again...") ... thanks to no continue. This last one is getting a thumbs up, but then I'd pause here and say "continue" can be easier on the eyes. It's unambiguous where it takes you, in contrast to having to scan on down the gauntlet, looking for possibly other open doors. "What happens next" should not require scanning ahead too far. Help us not to get lost. Be a civic-minded coder. I'm thinking of a programming style that advises two things: (a) if you use a while condition that's variable, that's expected to change, then your goal should be to always exit because of that, i.e. that should be your only exit point. Even if some other criterion suggests exiting, you have the option to flip that "lid" at the top, to crack that front door, and bounce the ball out. (b) which is why 'continue' is your friend. You are showing the user where your 'break' statements are, except you don't use "break" statements, as you've given a non-constant condition, and your aim is to make that your ONLY exit point. In short: never use break to exit a while loop unless your condition is while True. Instead, always flip the condition and exit through the font door. However, as soon as I make that rule I can think of good reasons to break it. The other programmers in the room are shaking their heads. Won't we lose information, needed elsewhere in the program, if we "artificially" force a True condition to False. Aren't we, in effect, lying? That concern could be addressed. Keep all the info true, just treat the "lid condition" (it "keeps a lid on it") as a flag. Go ahead and remember the user's guess. allowed = 5 tries = 1 exit = False while not exit: # no other way out guess = int(input("Guess?: ") if guess == secret: print("You guessed it!") exit = True # instead of break continue print("Nope, try again...") tries += 1 if tries == allowed: print("You've maxed out") exit = True continue I think we all understand the main issue: writing reader-friendly code, and rules for doing so. There's something comforting about approaching a while loop and knowing its not a leaky sieve, riddled with back doors, maybe even an exit( ) time bomb. But in the recursion world we want a minimum of two exits usually: when another round is called for versus when we've "hit bottom". Can we have it both ways? Conclusions: Lets not be too hasty with rules of thumb and: Lets keep the reader in mind when writing code. Just because the interpreter knows to compute the flow unambiguously, doesn't mean all ways of writing it are equally reader-friendly. What may seem a gratuitous gesture, an unnecessary flourish, may actually promote reader comprehension of your code, and that should be a goal as much as satisfying the interpreter. Kirby

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xturtle online via processing.js !?
by Jurgis Pralgauskis Sept. 27, 2012

Sept. 27, 2012

Hi, I am struggling around with interactive online py tutorials with https://launchpad.net/projects/intro-to-code (ith might become securely sandboxed soon, as pypy made it possible http://blog.sandbox.lt/en/WSGI%20and%20PyPy%20sandbox :) but one more thing is I'd like to let access xturtle functionality online - one possible way could be triggering tkinter to save its canvas to ps, and then convert them with imagemagic and show via web (animated gif or static) - but if pyjamas can render GUI for js (http://www.google.lt/search?&q=pyjamas+python ), mayby there is a way to **translate turtle commands to processing.js analogues** http://ejohn.org/blog/processingjs/ would it be difficult -- how do you think? -- Jurgis Pralgauskis tel: 8-616 77613; jabber: jurgis(a)akl.lt; skype: dz0rdzas; Don't worry, be happy and make things better ;) http://sagemath.visiems.lt

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first thoughts after OSCON
by kirby urner July 21, 2012

July 21, 2012

I've been to a number of OSCONs in my day, this being the 2nd wherein a participated behind the scenes on the talks selection committee, a pretty big commitment actually. I've also been a speaker, which is pressure of a different kind. OSCON is like a weather sensing device, very sensitive, but of patterns to complicated for the solo brain to grok, at least in the short time -- takes time to consider. Like this year the Cloud was big, with both Rackspace and HP about to get more public about their support for the OpenStack solution, which is very much a Python project, which is not to say Java can't be spun up in a virtual server just like anything else i.e. a commitment to Python as a platform language has nothing to do with limiting the freedoms of developers. Yes, we have a lot of Java programmers out there, thanks in large degree to a chapter wherein people went gaga for Java, especially in CS. And why not? It's a good and capable language. I worked at upping my level of appreciation for Go, no not the board game, the computer language. Yes it's open source and yes the talks and tutorial were well attended. I bought a book on Go as well, got it compiling on the Air. Could there be an implementation of Python in the Go language someday? That was my first question when Go started to get press, whereas the more computer illiterate were asking dumb questions like was Go the new Python killer. One's a system language the other's an agile. If history is any guide, there'll be be a GoPython someday. The Python and Perl tracks were both strong this year. You can't beat Damian Conway for drawing an audience. I'm a huge fan of Perl mongers. Sorry but that divide and conquer thing didn't work. We agiles are soul mates. OSCON got going thanks to Perl. What was kinda weird though was the education track in F-151 (kinda of like Area 51). The Common Standards buzz is a new one at OSCON, reminiscent of OLPC in terms of reaching a peak, feeding a frenzy, but I didn't sense the same levels. To be fair though, I didn't make it to either Texas Pycon, when OLPC was flying high. Pearson was there, and the Shared Learning Collaborative. http://www.oscon.com/oscon2012/public/schedule/detail/26434 What were they there for, mostly? To recruit? To share source code? To attend others' talks? These are questions to take back for further analysis. I guess one could ask a similar question about O'Reilly School of Technology, but no, not really, as (a) OST presented no talks and (b) we're just O'Reilly Media (part of) anyway, but with a Red Leaf logo, so we're an expected presence, with an already obvious agenda. In the case of the FERPA talk, it sounded like university admin might like more help with their dino sinking ship codebase, and I agree, they could use some. No question. What I took away from my brief work with Portland State (vicariously, not a direct contract) was that universities should do a lot more to eat their own dog food when it comes to administrative software. Start from the open source "clay" the real world economy uses, and take this as a teaching opportunity, with lessons about how closed data is still quite possible in this environment and in fact security is more robust as computer literacy improves across the population. I look forward to more university presence someday. They should be getting their faculty from us. We do STEM, not just computer science. The focus on outdoor sports, quantified self, camping (for real), planting sensors and enviro-cams around the world (oreilly/animals) is already well entrenched. The idea this is a group of cola drinking nerds eating pizza in windowless basements is way too 1970s. If that's your picture, time to hit fast forward on that antique VCR of yours. Kirby

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Education Room (Pycon 2013)
by kirby urner July 13, 2012

July 13, 2012

Vern and I have been chatting off list about his plans for an Education Room (ER? -- name collision) at Pycon 2013 (US). I've been thinking of exhibits, independently of the poster space, giving a sense of Python's span, as well has history, vis-a-vis the education systems. We've talked about Raspberry Pi and the RaspberryJam meetups these inspire, and OLPC -- I thought we should exhibit an XO tablet or two, running Sugar. Could we have those as prizes? Vern talked about his sense, chatting with educators, that we still lack a great set of resources for K-12 use. 'Mathematics for the Digital Age' is great, but couldn't we have more along these lines? 'How To Think Like a Computer Scientist' has also come a long way since Jeffrey Elkner helped bring it into Python culture, where it has remained. http://www.greenteapress.com/thinkpython/ I find myself recommending it to students pretty often. Regarding the future of Python in K-12, I think there are other discussions going on that will have an impact. STEM is a buzzword these days, but more than that it's the old school idea of a more integrated curriculum, wherein S, T, E and M have much less of a "standalone" or "stand offish" attitude. For quite awhile, I was hoping to get a blend of CS and math topics (like in 'Digital Age') accepted for math credits in the State of Oregon. I wasn't the only one with this hope. We had that workshop / planning meeting about it 3 years ago now. [1] The "Digital Math" or "Computational Thinking" or Discrete Math" topics were floated. I was pushing a 4 year track parallel to established "analog math" so we could have some green field development. That's still a useful vision for me, but I've more recently been attracted to STEM as a way to bring more Python in particular into more student spheres. The idea of a machine as a "formal system" is strong enough to keep the math purists from retaliating too concertedly. It's not like we're getting off topic.[2] We shall see. I joked we should call it the World Domination Room in light of Python's evident success, a tongue-in-cheek allusion to a perennial theme within free software and open access movements. Speaking of World Domination, Michelle's experiment in an all-mostly women Python class went well per reports, with more maxed out sessions already scheduled. The PSF has been financially supportive. I joke that a lot of my students might be veiled when in public, given the distance ed protocol.[3] I evaluate between 100 - 200 projects and quizzes a day, from around the Global U. Anyway, some brain storming on the big picture and how it's going might help us steer the direction of the Education Room in 2013. Feel free to share overview. Kirby [1] Chris Brooks went on to WebMD and I lost touch with SAO, so I'm not sure if anyone meets about this still. I've stopped getting those emails. [2] http://www.earlham.edu/~peters/courses/logsys/machines.htm [3] http://worldgame.blogspot.com/2012/07/ppug-2012710.html ("perhaps some of them veiled in Tehran")

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more pix of Raspberry Pi
by kirby urner July 13, 2012

July 13, 2012

Steve Holden is fresh back from the UK and had one of these in his pocket (yes they're quite tiny). Had it working in studio within minutes: some happy tweeting across the room. Steve Holden ‏@holdenweb The @Raspberry_Pi looks pretty neat projected on my living room wall. Pictures coming courtesy of @thekirbster 5m Kirby Urner Kirby Urner ‏@thekirbster @holdenweb here's the blog post, w pix http://controlroom.blogspot.com/2012/07/from-open-bastion.html Kirby

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Re: [Edu-sig] Edu-sig Digest, Vol 108, Issue 1
by Marianne McKenna July 9, 2012

July 9, 2012

I will be out of the office today. If you need immediate help please contact the computer center. Thanks.

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Re: [Edu-sig] guide to learning decorators
by kirby urner July 9, 2012

July 9, 2012

Re: http://www.amazon.com/Guide-Learning-Python-Decorators-ebook/dp/B006ZHJSIM I got the Kindle book on Python decorators. Quite inexpensive. I didn't give it my highest rating though, for two reasons: (a) there's some representing that an exhaustive treatment of the function arguments and parameters topic, but the use of * (asterisk) on its own, to section off keyword-only parameters, is not mentioned and (b) the authors hint at the many useful and wonderful things decorators might do, but are somewhat shy on examples. One would think just a few more pages of clever examples would round out the treatment. Other than those two omissions, I thought it was pretty strong. The main goal was to get to where your decorator function might itself take arguments, what that means. There are no examples of using a class as a decorator that I recall, nor of decorating a class. I should double check that. Kirby

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