Mailman 3 November 2014 - 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

8 17

Re: [Edu-sig] Getting more involved with education and the PSF...
by Jeff Elkner Jan. 9, 2015

Jan. 9, 2015

Two questions: 1. Andre, what do I need to do to begin maintaining that page? 2. Is there anyone in this thread not on edu-sig? My next reply will go only to the list. On Thu, May 22, 2014 at 10:09 AM, Jessica Nickel <jessanickel(a)gmail.com> wrote: > Sounds like a plan. I would be happy to talk with Selena about the work to > bridge the gap between k-12 educators and Python programmers. I was a k-12 > teacher for 10 years (music) and I have been working in schools with my > program to teach python coding to kids for the past year and a half, so I do > have some experience in that area. > > > > > On Thu, May 22, 2014 at 10:02 AM, Jeff Elkner <jeff(a)elkner.net> wrote: >> >> Great! So it seems we have two short term goals: >> >> 1. Get someone to agree to maintain the website (I'm volunteering if >> there isn't anyone else chomping at the bit to do it). >> 2. Reach out to Selena Deckelman to help her with her efforts to >> bridge the gap between developers and K-12 teachers (a noble goal >> indeed!). >> >> Do we agree that edu-sig is the sensible place to hold this conversation? >> >> If we do, can we ask Selena to join the list if she is not already >> there? I'll also encourage folks like Lee Harr (cc'd here), the >> creator of the wonderful Pynguin environment >> (https://code.google.com/p/pynguin/) to join the list and the >> discussion. >> >> On Thu, May 22, 2014 at 8:01 AM, Naomi Ceder <naomi.ceder(a)gmail.com> >> wrote: >> > One point of info I can add - the person you're thinking of running for >> > PSF >> > board is Selena Deckelman, who was on Nate's panel at the edu summit. >> > She's >> > been very into bridging the gap between developers and K-12 teachers. >> > >> > Naomi > >

6 14

computers and schools
by Christian Mascher Nov. 30, 2014

Nov. 30, 2014

Hi Kirby, > I think many students would be better served if the emphasis were on > creating for them a safe personal workspace, with plenty of bandwidth > to the outside world, with opportunities for 2-way interactions (so > not just receiving broadcast television, as in the "mindless consumer > couch potato" model of the late 1900s). > I know that many if not most of our students have exactly this environment at their home. But they don't use it much for learning. The average 14-year-old won't do much education-wise outside of some fields of special interest, if there isn't any pressure in form of exams and tests etc. Just talking about real students... > In a comfortable middle class household, Johnny already has a heated > bedroom with a desk, books, and computer, but has to leave this > workspace to rub shoulders with peers in a daycare setting we call > "school". I know quite a lot would rather stay at home and play the same computer games all day. Still waiting to see the masses who want to learn two foreign languages plus maths and sciences all on their own... (I know there always are some exceptions. I always wanted to learn more than what I learned at school, but even I did go to school nevertheless and probably would never have learnt Maths or French all on my own.) > > Said school may censor Youtube and/or otherwise block access to > information, so for many school-goers the experience of school is of > burning an expensive fuel to frequent a less information-rich > environment than their own comfortable bedrooms. > Well I get to see lots of real students, but when they open youtube in a computer lab at school, they never look at those wonderful educational videos. I encourage them to do so at home (maths is explained pretty much like at school, but with a pause and rewind button!), but many prefer to use their own time otherwise. > > Better that Sally should stay home and watch instructional Youtubes > about > math + programming approach to STEM. She just won't find that > at her local day care center. Why waste Sally's time? I haven't met many of Sally' s kind. Also: In many countries in Europe (in Germany for instance) homeschooling is actually forbidden for a variety of reasons. But apart from that: I do question the main assumption that not using a computer for a couple of hours each day is in any way damaging to the education. On the contrary I think it is higly unlikely that a large proportion of the youth in Germany would still learn English, Maths, some bits about Science and History at the same levels as today when they would be left to their own (computer) devices. Already in the present system the advantaged students are those who have educated parents, not those with the biggest computer racks at home. That problem would be amplified to the extreme, when education would be privatized in this way. My guess is: Only the very best 1-3% students would learn more or less about as much as now, because some kind of coach would be around. To paraprase Churchhill: Schools are lousy ecosystems for learning but we haven't found any practical better systems yet. How successful has the OLPC-project actually been? Any evidence beyond quotes and ideas from SciFi "The diamond age" ;-) ? Cheers Christian

2 1

Re: [Edu-sig] Reeborg update
by Laura Creighton Nov. 30, 2014

Nov. 30, 2014

In a message of Mon, 24 Nov 2014 11:48:45 -0400, Andre Roberge writes: >On Mon, Nov 24, 2014 at 11:41 AM, Christian Mascher < >christian.mascher(a)gmx.de> wrote: > >> Hi, >> >> I went there in a recent chrome on a laptop with a fairly small screen and >>> there are some rendering issues that make some of the controls unusable. >>> >>> >> I noticed the same with Nexus 7 (android) and firefox. On the desktop Ctrl >> + - usually makes things smaller and thus fit onto the screen (esp. editor >> right next to the world, so the controls below the world are visible), but >> on the android tablet that didn't help. >> >> These tablets are just to small for all the information and even firefox >> is different compared to its desktop version. > > >>From the beginning, my thinking was that anyone interested in doing some >programming was going to use either a deskop or laptop with proper >keyboard, etc., and thus a reasonably sized screen. > >Should I review this basic hypothesis? If so, does anyone have an idea as >to what minimum screen size I should be aiming to support? I'm not ever >planning to target tiny screens for smartphones and the like ... but if >only relatively small adjustements are needed to support "typical" tablets, >I could look into it. > >André Children all over Sweden are getting ipads, ruggardized from the school districts. They are 240 x 170 mm, and apple has done a very good job of convincing education officials that this is where the 'computer literacy' money should be spent. Some schools are bucking the trend and using Android tablets instead. They are typically '10 inch' screen but some '7 inch screens' as well are being used. The android market is fragmented, so what a 10-inch screen really is, width and height-wise varies, as long as 10 inches is on the diagonal, that is what they will call it. And the current trend in cellphones is to grow them like crazy, so the flagship models of a great many popular brands now support 6.5 inch screens. (Indeed, it is a bit of a chore to find a very fast phone with a smaller screen. Since I already own a 7-inch android tablet, I would like things much better if my phone could just stay a phone, and go back to the battery length times we had before we had smartphones ....) But I disgress. At any rate, for use around here ipad support would be required, and if you got things to work with a 7-inch screen a whole lot of other people would be happy. But that's just here ... Laura

4 4

CodeCombat online coding learning platform for Python and more languages (opensource)
by Jurgis Pralgauskis Nov. 27, 2014

Nov. 27, 2014

Hi, I tried it via my students (found on http://code.org/learn) http://codecombat.com/?hour_of_code=true . Neat pedagogical approach: - attractive graphics (for boys esp.) , - default coding language "python" :) - slow learning curve, - line highlighting, - some "simplified" syntax for python loops (instead of "while True", just write "loop") - didn't notice conditional statments so far ps.: Made with coffescript https://github.com/codecombat/codecombat -- Jurgis Pralgauskis tel: 8-616 77613; Don't worry, be happy and make things better ;) http://galvosukykla.lt

2 1

Re: [Edu-sig] Reeborg update
by Laura Creighton Nov. 24, 2014

Nov. 24, 2014

By the way, around here I get to read a whole lot of stuff the import of which is that just as writing and penmanship are no longer things that teachers need to focus on (because everybody types things, these days), typing is about to get the axe as voice recognition is getting up to speed. So people will not have to learn how to type, they will just talk their essays, etc. into their tablets. I think that this may work fine for dictation, but right now I shudder at the thought of modifying code that way. But this is what the future is supposed to be, or so we are being told ... Laura

1 0

Re: [Edu-sig] Reeborg update
by Laura Creighton Nov. 24, 2014

Nov. 24, 2014

Well, getting the specs for an Ipad air is easy, any apple site has that. And should Apple be as anxious to get ipads into Canadian schools as it was to get them in Swedish schools, getting a ipad for you to test on would just be a matter of calling your local apple rep and saying 'hey, I want to test my educational software and get it to work on an ipad'. If things work over there the way you do here, you would get an ipad or 2 in the mail over the next few days. Laura

1 0

CS contest for grades 3-5
by Litvin Nov. 24, 2014

Nov. 24, 2014

This winter the Continental Mathematics League will, for the first time, offer a computer science contest for elementary school kids, grades 3-5. The contest consists of three "meets," 6 questions for 30 minutes in each meet. All the questions are "unplugged" -- no computers are needed. Please spread the word to elementary school teachers you know. More info and the registration form at http://www.continentalmathematicsleague.com/applications/computer.pdf or http://www.skylit.com/cml35.html. Gary Litvin

1 0

Re: [Edu-sig] Reeborg update
by Lee Harr Nov. 24, 2014

Nov. 24, 2014

> Actual world where program can be run: http://reeborg.ca/world.html It looks very interesting. One thing -- not sure how important this is with most people using larger screens these days -- I went there in a recent chrome on a laptop with a fairly small screen and there are some rendering issues that make some of the controls unusable. Once I switched over to my desktop, the issues were not apparent. I am definitely going to have some students give your tutorials a try. Thanks!

3 2

Re: [Edu-sig] alluding to earlier thread re "pythonic" versus "obtuse"
by Lee Harr Nov. 23, 2014

Nov. 23, 2014

> ext = os.path.splitext(fn)[1][1:] I find this line a bit ... wider than I prefer. With these functions that return two things, I will often do... root, ext = os.path.splitext(fn) ext = ext[1:] Two lines instead of one, true, but especially when working with students it illustrates one of python's cooler features (unpacking). If I will not be using the root portion, I might do... _, ext = os.path.splitext(fn) ext = ext[1:] I sat and thought about using a different name for the first ext -- maybe dotext or dot_ext, but I don't think it is necessary.

1 0