Mailman 3 August 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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Sample letter from summer camp instructor parents / guardians
by kirby urner 25 Aug '17

25 Aug '17

I currently have six campers in my current class. We meet for three hours a day for five days. They're junior high to high school age, grades 8 - 11. The email below gives the flavor what how we're organized. Coding with Kids has spread to several US cities. The instructor has quite a bit of latitude. We're currently using Codesters and in some cases Cloud9. In the mornings I have a younger group and we do MIT Scratch for three hours. A lot of students start in Scratch and continue in Python. When it comes to HTML + CSS + JS, we move to codepen.io That's a snapshot of the state of the art in Greater Portland, when it comes to augmenting established school programs, both after school and during summer vacation time. Kirby ---------- Forwarded message ---------- From: Coding with Kids <info-portland(a)codingwithkids.com> Date: Wed, Aug 23, 2017 at 11:25 AM Subject: Greetings from summer camp instructor, Python class 2017 Summer Lake Oswego - BiC 16318 Bryant Rd Lake Oswego OR 97035 Greetings all -- Thank you for sharing your camper with our group. We're using Codesters, modeled after MIT Scratch, to introduce the basics of Python3, a general purpose computer language used a lot by professionals in many walks of life, not just by computer programmers. Mostly they focus on their own projects, getting individualized assistance from myself or from peers, thereby gradually building up familiarity with this sprite-based development platform, conducive to designing simple games and telling stories. Sprite objects are like puppets or comic book figures and come with methods for moving, sharing talk balloons, detecting collisions with others. Encourage your camper to show you what it's like, or come a little early on Friday for an opportunity to see what they've been working on. I punctuate their hands-on experience with projected presentations about what Python looks like outside of Codesters. Yesterday, for example, we took a look at the Anaconda distribution of Python, which comes with its own code editor (Spyder) and Jupyter Notebooks, a system for creating web pages that double as interactive Python worksheets. I want them to have more context, a better understanding of Python's role in the real world. I have Juper Notebooks saved on Github which they're welcome to study at their leisure: https://github.com/4dsolutions/Python5/ Today I will show them Google Blockly and Repl.it, further expanding their horizons. Blockly is a Scratch-like block language which automatically translates the jigsaw-puzzle looking programs into other languages, including Python. Repl.it (repl = read, evaluate, print, loop per Wikipedia) provides a free Python interpreter in the cloud, once a user has created login credentials. I've got several examples in my personal stash: https://repl.it/@kurner Our goal is to make programming a fun, recreational activity, engaging as an end in itself, so that moving up the learning curve does not seem an onerous chore. If your camper has more specific goals regarding Python in particular, please encourage them to talk with me, or feel free to send me email. Please feel free to share this communication with them. I've used Python for many years and teach it to adults from many walks of life. What's great about Python is it's an elegant implementation of the object oriented way of thinking, and therefore smooths the path to gaining proficiency with other object oriented languages in addition to Python, such as Ruby, Java and JavaScript. Kirby Urner 2017 Summer kirby.urner(a)codingwithkids.com

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Announcing robotbenchmark.net
by Olivier Michel 23 Aug '17

23 Aug '17

We just launched https://robotbenchmark.net to allow everyone to program simulated robots online with Python. Video announcement: https://www.youtube.com/watch?v=S0k0cJb_Mus Robotbenchmark offers a series of robot Python programming challenges that address various topics across a wide range of difficulty levels, from middle school to PhD. Users don't need to install any software on their computer, cloud-based 3D robotics simulations run on a web page. They can learn programming by writing Python code to control robot behavior. The performance achieved by users is recorded and displayed online, so that they can challenge their friends and show off their skills at robot programming on social networks. Everything is designed to be extremely easy-to-use, runs on any computer, any web browser, and is totally free of charge. I believe his tool has a great potential for teaching Python, as 3D simulated robots are very appealing to students. We would love to receive your feedback at info(a)robotbenchmark.net. Cheers, -Olivier

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Localized keywords library for learning Python
by Sebastian Silva 17 Aug '17

17 Aug '17

Hi! I enjoy teaching Python to kids and have just been reading André Robergé's wonderful Reeborg tool and documentation and have appreciated two details on his approach to Python: The introduction of "repeat :" keyword: http://reeborg.ca/docs/en/basics/repeat.html And the availability of statements in french: http://reeborg.ca/docs/en/basics/library.html#reeborg-can-understand-french This reminded me of a library that was shared I think on this list, for translating the basic Python keywords to a foreign language? Could somebody please share this link again? I'm failing to find it. As the author of a Python learning IDE i'm considering to adopt some of these measures to help scaffold working knowledge full Python... I appreciate your thoughts and references, Sebastian

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Announcement: new version of Reeborg's World
by Andre Roberge 16 Aug '17

16 Aug '17

After more than a year of rewriting, reorganizing and adding features, a new version of Reeborg's World (http://reeborg.ca/reeborg.html) is finally available. I have done some fairly extensive testing ... but there's nothing like having other users testing it to discover bugs. I'm hoping to quash any remaining bug by September, in time for the new school year. Reeborg's World takes the basic Karel the robot idea from Pattis and builds upon it. As I started to write documentation explaining the new features, I quickly realized that there was a lot of things to described … so many in fact that it has become a book titled *Reeborg’s World: a Teacher’s Guide*. The book is not finished yet but it is available online. https://aroberge.gitbooks.io/reeborg-s-world-advanced-world-creation/conten… I would love to get your feedback on either the site itself, or the book, or both. Cheers, André

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comments on a Python expert Youtube / Python2 vs Python3
by kirby urner 12 Aug '17

12 Aug '17

I just listened to the first 18 minutes, 7 seconds of this PyData talk: https://youtu.be/7lmCu8wz8ro What Does It Take To Be An Expert At Python? The speaker, James Powell. has an excellent and engaging style. However, two things: * the degree of the polynomials he's showing is 2 in both cases, not 3 * __call__ makes perfect sense with a polynomial: feed in a value for x, get the result. On another topic: In my inhouse memos (Coding with Kids) I encourage Python2 and Python3, for 2.x series and 3.x series respectively. We have the precedent of CPython (a prefix) so could say CPython2 unambiguously. Django3 etc. is also suggested. Codesters.com works to emulate Python3. The turtle is in trouble at the moment, unable to draw a circle reliably, especially when moving backwards. Regarding "dunder methods" (special names), calling them "data model" methods is not a bad idea. I still like to call them __ribs__ thinking of snakes (pythons) being hollow __rib__ cages. We're talking about how we give our classes a backbone of neural arc behaviors. Kirby PS: one of my polynomial classes from ages ago: """ Really simple Poly (polynomial class) Example usage: >>> from simppoly import Poly >>> p = Poly([1,2,0,0,3,-4]) >>> p (1 * (x**0))+(2 * (x**1))+(3 * (x**4))+(-4 * (x**5)) >>> p(10) -369979 """ class Poly(object): def __init__(self, coeffs): """ Coefficients in order of increasing degree, 0 where necessary """ self.coeffs = coeffs def __call__(self, x): """ Triggers evaluation of string representation for 'x' = x """ return eval(repr(self), {'x':x}) def __repr__(self): """ Build a string representation, low to high degree, skipping 0 coefficients """ monomials = [ '(%s * (x**%s))' % (c,e) for c,e in zip(self.coeffs, range(len(self.coeffs))) if c<>0] return ' + '.join(monomials)

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