Mailman 3 September 2016 - Edu-sig

a short essay about programming
by kirby urner 08 Dec '22

08 Dec '22

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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MineCraft with Python
by Jurgis Pralgauskis 04 Dec '22

04 Dec '22

Hi, intro: many kids like MineCraft :) probably you know/heared of MineCraft Pi https://www.raspberrypi.org/learning/getting-started-with-minecraft-pi/ But there seems to be Py for real MC http://coderdojotc.readthedocs.io/projects/python-minecraft/en/latest/ http://www.instructables.com/id/Python-coding-for-Minecraft/ PS.: a nice article (from js4MC world) https://github.com/walterhiggins/ScriptCraft/blob/master/docs/YoungPersonsG… -- Jurgis Pralgauskis tel: 8-616 77613; Don't worry, be happy and make things better ;) http://galvosukykla.lt

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turtle coordinates: Y increase downards - as in most graphics API?
by Jurgis Pralgauskis 02 Jul '18

02 Jul '18

Hi, usually in computer graphics Y is counted to increase downwards. I casn do it with: setworldcoordinates(0, 400, 600, 0) but then, "right(..)" turns to the left :/ I could swap: right, left = left, right but on errror I get a bit misleading message >>> right() Traceback (most recent call last): File "<pyshell#10>", line 1, in <module> right() TypeError: left() takes exactly 1 argument (0 given) I thought to make this hack for kids, so better clearer error msgs... Any Ideas? Thanks :) -- Jurgis Pralgauskis tel: 8-616 77613; Don't worry, be happy and make things better ;) http://galvosukykla.lt

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more Silicon Forest slant...
by kirby urner 27 Sep '16

27 Sep '16

If you wanna get more nitty gritty details on our work in Portland, and Oregon (a US state, Portland not the capital), here's a recent link, a good trail head: http://mail.geneseo.edu/pipermail/math-thinking-l/2016-September/000785.html Looking ahead to Pycon 2017: Those who say "Pythun", UKers mostly, are already ahead in saying "Orygun" the way we do. Portlanders make fun of out-of-towners who say "Ore-Gone" as they say "Poly-Gone" (as in "Where has Polly gone?"). Our insiders say "Oregun" as in "Where did Polly leave her gun this time? What a ditz!"

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a thirty minute interview of Kirby (courtesy of Nepris)
by kirby urner 27 Sep '16

27 Sep '16

If curious, here's a trail head with the actual link: https://twitter.com/4DsolutionsPDX/status/778998480874250241 This was my session with the Austin Texas high school kids, mentioned here: http://worldgame.blogspot.com/2016/09/talk-like-pirate.html Kirby

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update from Portland...
by kirby urner 17 Sep '16

17 Sep '16

Greeting edu-sig subscribers -- News from PDX (Portland) is: * I've been taking R-Pi around town, showing off this nifty "Py machine", great intro to bash shell world http://worldgame.blogspot.com/2016/09/wanderers-201696.html * Hedron, local Maker Space, exhibitor at Maker Faire, 3D prints polyhedrons our math teachers need... http://controlroom.blogspot.com/2016/09/art-car.html * ...Python already has the computing culture to make itself known through Jupyter Notebooks etc., yay http://4dsolutions.net/ocn/ * I'm back to teaching night school next week, Python 3.x in five weeks (40 hours). If you visit Portland: Python User Group meets c/o @UrbanAirship in Meir & Frank building on SW Everett. The group is well-organized and active. PDX Code Guild, Flying Circus, is every Monday (almost) and happens in a Python-based code school but features talks more all over the map. 2626 SW Corbett. Calagator is our most used geek events resource: http://calagator.org/ Also, Mercury just put out a helpful newcomers guide: http://www.portlandmercury.com/Newcomers-Guide-2016/2016/09/14/18565180/a-n… Kirby

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