Mailman 3 January 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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Turtle
by Marcin Wojciechowski 12 Feb '17

12 Feb '17

Hello, I teach computer science in elementary school. Looking for information on turtle. I like very much and would like to apply it in the classroom. Marcin Wojciechowski http://marcinwojciechowski.edu.pl

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update from Silicon Forest
by kirby urner 01 Feb '17

01 Feb '17

Greetings from Silicon Forest to this mostly-quiet list. Perhaps listservs in general have been overtaken in many cases, by technology with a higher bling factor. Or maybe it's that listservs (mail lists) are not an obvious vehicle for blatant advertising whereas Twitter, Facebook, Google Plus and such, all have obvious ways for marketers to break in. Glad to see about the new release of the physics engine.[1] Portland has been under a blanket of snow, so the Winter term is off to a slow start. That's with regard to an after school program I help staff, more another time (CwK [2]). The public school system in Portland is a big fan of MIT Scratch, did I mention? Where to next after that, if MIT Scratch is how you started? There's more than one way forward naturally. However if you've started in the cloud and are used to accessing the same work from multiple devices, then you'll probably want to keep working that way, at least sometimes. Have most here heard of Codesters already? https://www.codesters.com/ Codesters provides a platform very like MIT Scratch, by deliberate design, providing continuity of concepts and skills (sprites and backdrops, drag and drop tools, sorted by topic) into a Pythonic environment. https://youtu.be/Q1hj5XvrfTw I used the snow days to study up on Finnish history a little, with a spike in activity on Facebook where I see some of you. Looking forward to a visit from former PSF director and former Pycon tycoon (used for alliteration) Steve Holden in a week or so. Many readers here know him. He's a UKer now living back in the homeland, who is likewise very at home in the US, had a cool office and apartment (separate addresses) just blocks from here in recent years. Speaking of Pycon, I signed on as a possible co-speaking at two Pycon talks. Charles Crosse [3] has devised an ingenius business plan he wants to open source, plus (and this is what's impressive) a working prototype he's actually field tested with his own family. Basically, it's a way for parents to set it up for unsupervised learning where junior gets more "lives" (time on the Internet) in exchange for choosing from "pre-approved activities". Translation: "if you do your math homework, you'll get more time on the X-Box" Whether the proposals fly or not (as talks), I'm optimistic about the model. The prototype uses a Raspberry Pi as a stand-in router. That's the shut-off valve. If you don't do your math homework, the router stops feeding you lives and you X-box loses its net connection (there's a GUI and everything). In addition to Codesters, our program uses Cloud9. I continue to showcase thekirbster.pythonanywhere.com as a somewhat functional CRUD application (the skeleton is there) using Flask + Jinja2. Very minimalist, just showing what a bare bones web application might consist of. You've got the idea of "front and back door APIs" i.e. a front door for human eyeballs, a back door for other computers using an API. We could call it a "service entrance" like when trucks back up to the warehouse to load/unload goods (but in this case using JSON). Kirby [1] I've been yammering about physics education Youtubes on that list for physics teachers I frequent, closed archive (for now). Behind those Youtubes (animations) may be a physics engine. [2] https://www.codingwithkids.com/#!/afterschool?show=locations&region=2 [3] http://coffeeshopsnet.blogspot.com/2016/09/internet-aware-lcds.html (another project) http://mybizmo.blogspot.com/2016/10/go-by-train.html (picture of Charles, bottom)

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Adaptive Python Course + 10k$ Contest of content
by Jurgis Pralgauskis 26 Jan '17

26 Jan '17

Hi, nice concept :) https://stepik.org/course/Adaptive-Python-568/?utm_source=newsletter&utm_ca… and 10k$ Contest of courses http://adaptive.stepik.org/ :) -- Jurgis Pralgauskis tel: 8-616 77613; Don't worry, be happy and make things better ;) http://galvosukykla.lt

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Python Physics Sandbox released
by Jay Shaffstall 12 Jan '17

12 Jan '17

I'm very pleased to announce the general release of a Python physics sandbox targeting students in intro programming courses. We teach Python as a first language here and a physics simulation has long been one of the students' favorite labs. But the simulation we were using, while easy to use, was pretty limited and only worked in one particular IDE. So I wrote PyPhysicsSandbox, a thin wrapper around pymunk. The sandbox allows students to construct more sophisticated combinations of shapes and joints and interactivity with the user. It should also work in any environment that allows installing libraries to Python using pip. The code lives here: https://github.com/jshaffstall/PyPhysicsSandbox It's freely available for use in your own classes. Jay

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