Mailman 3 October 2017 - 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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Re: [Edu-sig] when and why should kids learn Python?
by kirby urner 29 Oct '17

29 Oct '17

On Sat, Oct 28, 2017 at 1:44 PM, David MacQuigg <macquigg(a)gmail.com> wrote: << ... >> I just hate to see what could have been a critical mass of users offering > an alternative to Java, a much better alternative as an introduction to CS, > losing that opportunity because there is no agreement on a simple > alternative. Oh well, most students will end up with Java anyway, so maybe > learning with all those useless semicolons will make the transition easier. > > Thank you, yes, I share your view that Ruby feels more like Perl and markets itself versus Python with somewhat hollow slogans like "Ruby makes programmers feel happy" (it's all about how it "feels"). AP CS seems stuck in the crufty past given a main rationale was to pick a language actually taught at the college level. That used to be Java, but is now Python so much more so. https://www.quora.com/Why-does-AP-Computer-Science-A-teach-Java-and-not-Pyt… I'm always in favor of learning at least a couple languages, even if #2 is mainly for contrast. One's mastery of X improves when one has experience with ~X. Learn Python and Ruby both? But learn one to a higher level? Clojure? As this other thread points out, there's a new AP CS Principles course (CSP) which Code.org and others are tackling, in principle language agnostic. JavaScript is another contender as a first language, especially in light of all the recent revisions (making it seem more like Python :-D). https://computinged.wordpress.com/2014/08/03/python-is-the-most-popular-int… Since the posting above (2014) -- about how college intro courses don't use JavaScript as a first langauge --came at least Stanford's doing so: https://www.theregister.co.uk/2017/04/24/stanford_tests_javascript_in_place… I think Harvard's CS50 is a good example of how Python has replaced Java in terms of sharing the big picture. I refer people to the lectures on Youtube, Week 8 in particular. https://youtu.be/5aP9Bl9hcqI Kirby

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when and why should kids learn Python?
by kirby urner 28 Oct '17

28 Oct '17

This Codepen is dual purpose in that the company I work for (one of them) teaches with it, so I can say I'm promoting / recruiting for one of our other (not Python) classes. https://codepen.io/pdx4d/full/RjwrvG/ Ironically though, I'm actually coming to the conclusion that the "game card" is over-played, by which I mean, we take kids' love of computer games and suggest their hearts' desire is just a heart beat away. But that's not so: knowing how to code well enough to make games of real interest (to them), takes time. Lots of other tasks are more realistic: making art, slide shows, ads, stories... along with rather simple game-like activities. But you've gotta focus on a lot of syntax and semantics first. We need to be up front about the need for concentration and practice. Programming is "hard fun". You don't learn Python in just a few hours, especially not if it's a first lexical (not block-based) language. The tiny games and game fragments that are within range, *may* be enough to galvanize an ongoing interest in coding, but in a minority of cases. Instead there's a sense of betrayal, of bait and switch, as "game development" is oversold. Simple animations would be fine if that's what we offered. Storyboarding and cartooning with Python -- makes sense. But the games they play incessantly, day in and day out, are often multi-user, plus they're slick and well thought-out. I'm more of the school of thought that if Learning to Code is to become a mature aspect of the everyday curriculum, it'll need to merge in a lot of math topics. Bootstrap is already a big step in this direction. I see many signs that this merger is well underway. In sum, I'm for using Python when there's related age-appropriate math we might code around, such as the Sieve of Eratosthenes or prime factoring. Functions, plotting, geometry... all good. I'm against using Python as a "game development platform" with kids who are too young to understand that their favorite computer games are not good examples of what they'll be able to code any time soon. My belief is CS has for so long has been an after school "computer club" activity, that it still feels a need to pander, sell itself. Math, on the other hand, is a required non-elective subject between you and a high school degree. Now that coding has emerged as more of a priority in our culture, thanks to many factors including industry pressure, it's starting to count towards math credit in some cases, and maybe becoming a tad less obsequious in recruiting? The curriculum at Stuyvesant High School in New York City seems appropriately serious, not all that game-oriented. They're more Racket / Scheme based than Python, and were that way prior to Bootstrap and/or CS4ALL. They do have some Python content though, judging solely from their website. I followed their link, under resources, to http://codingbat.com/python which I'm liking, though it's small. Kirby

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strategies for teaching Python
by kirby urner 04 Oct '17

04 Oct '17

Given I'm spending 3-4 days a week with 5th & 6th graders, teaching them Python, I'm looking for ways to sync with what Common Core says they should be learning math-wise. They general strategy here is to look for topics already in the curriculum and develop coding skills around those topics. Turns out that prime versus composite is important at that age, and the classic algorithm used to teach that is the Sieve of Eratosthenes. Most coders have written at least one of those. Since we're transitioning from block-based MIT Scratch with not much keyboarding, to full-fledged lexical Python, I'm thinking to assess facility with keyboarding (typing) by having them hand-enter a Sieve, and running it to check for any syntax errors. While we're still doing natural and whole numbers it makes sense to look at other number series as well, ones we can explore using very simple Python. Triangular and square numbers, then polyhedral number sequences, such as successive shells around a nucleus. 1, 12, 42, 92... http://oeis.org/A005901 (note link to my website under links) https://github.com/4dsolutions/Python5/blob/master/STEM%20Mathematics.ipynb Pascal's Triangle is an important hub for studying number sequences. It even embeds the Fibonacci Numbers. These are the kinds of ideas I've been circling for some years. http://4dsolutions.net/ocn/numeracy0.html What's new is I'm getting more opportunities to test them in real world classrooms. Coding with Kids is keeping me busy. With my adult students, I'm looking at what I call the "Five Dimensions of Python" wherein they expand their awareness of the language, from keywords (dimension 0) to 3rd party ecosystem (dimension 4). http://mybizmo.blogspot.com/2017/09/five-dimensions-of-python.html (links to another Jupyter Notebook) I've finally figured out that Codesters (codesters.com) is about Python 2.7, not Python 3.x. I've been confused on that score. Given cryptography is playing a more important role in everyday eCommerce, it makes sense to beef up some of the Number and Group Theory aspects of K-12. I've been arguing on math-teach that right when we introduce primes versus composites, we should likewise introduce Fermat's primality test. http://mathforum.org/kb/message.jspa?messageID=10241002 http://mathforum.org/kb/thread.jspa?threadID=2883906 Kirby

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Browser-based instruction
by Catherine Devlin 03 Oct '17

03 Oct '17

Hi, educators, I'm thinking of teaching classes at our public library for folks who may or may not own their own computers. To that end, I'm trying to figure out the best way to provide them a hosted Python environment. The platform of my dreams would - Let them write and keep their scripts long-term - Allow installation of packages from PyPI - Not restrict outgoing web traffic - for instance, consuming web APIs is great for student projects, but many online environments restrict that use I don't know what's the closest to my dreams, but if anybody has relevant experience, I'd love to hear about it. Thanks! -- - Catherine http://catherinedevlin.blogspot.com

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snakify.org - one more interactive tutorial site
by Jurgis Pralgauskis 03 Oct '17

03 Oct '17

https://snakify.org/ with open content https://github.com/snakify/content -- Jurgis Pralgauskis tel: 8-616 77613; Don't worry, be happy and make things better ;) http://galvosukykla.lt

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