Mailman 3 October 2014 - 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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Re: [Edu-sig] Getting more involved with education and the PSF...
by Jeff Elkner 09 Jan '15

09 Jan '15

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 > >

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more mathematics for the digital age....
by kirby urner 29 Oct '14

29 Oct '14

''' (c) MIT License by K. Urner More playing around with NKS for a Gnu Math class using Python NKS = new kind of science (Wolfram) i.e. cellular automata (CA) ''' def make_rule(n): """takes 0-255 and returns rule dict""" the_rule = {} values = "{:08b}".format(n) for x in range(8): key = "{:03b}".format(x) the_rule[key] = values[x] return the_rule def transcribe(s, r): """takes a row s and returns a row based on rule r""" n = 0 max = len(s) out = '' while n < max-2: triple = s[n:n+3] out += r[triple] n += 1 return out def generations(s, r, n=1): """applies rule r to transcribed output, starting with s, n times""" for _ in range(n): row = transcribe(s, r) s = row yield row rule130 = make_rule(130) top = '000000000000010000000000000' the_gen = generations(top, rule130, 10) dots=0 print(top) while True: dots += 1 try: print("."*dots, next(the_gen), sep="") except: break

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Re: [Edu-sig] Edu-sig Digest, Vol 135, Issue 9
by Marianne McKenna 26 Oct '14

26 Oct '14

I am out of the office, today., October 21st I will try to respond to email as I am able. If you need immediate help, please contact tech support.

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Re: [Edu-sig] Edu-sig Digest, Vol 135, Issue 8
by Marianne McKenna 25 Oct '14

25 Oct '14

I am out of the office, today., October 21st I will try to respond to email as I am able. If you need immediate help, please contact tech support.

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Re: [Edu-sig] Edu-sig Digest, Vol 135, Issue 7
by Marianne McKenna 24 Oct '14

24 Oct '14

I am out of the office, today., October 21st I will try to respond to email as I am able. If you need immediate help, please contact tech support.

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Re: [Edu-sig] Edu-sig Digest, Vol 135, Issue 6
by Marianne McKenna 23 Oct '14

23 Oct '14

I am out of the office, today., October 21st I will try to respond to email as I am able. If you need immediate help, please contact tech support.

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Re: [Edu-sig] Edu-sig Digest, Vol 135, Issue 5
by Marianne McKenna 22 Oct '14

22 Oct '14

I am out of the office, today., October 21st I will try to respond to email as I am able. If you need immediate help, please contact tech support.

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Fwd: From Scratch to Real Python Code with our New Block Trinket!
by Jurgis Pralgauskis 21 Oct '14

21 Oct '14

pedagogically very good approach and technologically, seems very simple :) ---------- Forwarded message ---------- From: elliott(a)trinket.io <elliotttrinket.io(a)trinketio.mail.intercom.io> Date: Fri, Oct 17, 2014 at 10:36 PM Subject: From Scratch to Real Python Code with our New Block Trinket! To: jurgis.pralgauskis(a)gmail.com Hi Jurgis! I'm very excited to announce our new *Interactive Block Trinkets*: <https://via.intercom.io/c?url=https%3A%2F%2Ftrinket.io%2Flibrary%2Ftrinkets…> Inspired by Scratch <https://via.intercom.io/c?url=http%3A%2F%2Fscratch.mit.edu&h=0d6fadf2a241cc…> and Code.org <https://via.intercom.io/c?url=http%3A%2F%2Fcode.org&h=bb9eb1eb904a1867195a8…>'s Hour of Code <https://via.intercom.io/c?url=http%3A%2F%2Fcsedweek.org%2F&h=542b72242575c0…>, these Trinkets take typing and syntax out of the equation of teaching and learning Python. But unlike previous block-based tools, *they're generating real Python underneath*! This lets students move into the world of real programming languages and bring their computational thinking skills along. <https://via.intercom.io/c?url=https%3A%2F%2Ftrinket.io%2Flibrary%2Ftrinkets…> >From the tests we've done with teachers and students, seeing the relationship between familiar blocks and unfamiliar code helps demystify code and accelerates the learning process. We can't wait to see what you do with this new too! Get Started with Blocks Today Click Here <https://via.intercom.io/c?url=https%3A%2F%2Ftrinket.io%2Flibrary%2Ftrinkets…> to see the example above, which you can easily share or copy it to your account! Or, if you're feeling creative, here's how easy it is to make your own: - Log in to Trinket <https://via.intercom.io/c?url=http%3A%2F%2Ftrinket.io%2Fhome&h=41b84490bc49…>, click the New Trinket Button, and select *Blocks *as your Trinket type - Grab blocks from the palette to build your Trinket - Click Save and you've made your Trinket! Now share a link or embed the Trinket anywhere, such as Google Sites <https://via.intercom.io/c?url=http%3A%2F%2Fblog.trinket.io%2Fhow-to-google-…> - Click the *View Code* button at any time to see what Python the blocks have generated In the coming weeks we'll be building a tighter integration with our popular Python trinkets. This will be a true end-to-end solution for getting students who know Scratch or other block-based languages hands on with real Python code. As always, I'd love to see what you create with these! Create or modify a Block trinket and reply to this email with the link. We'll feature the best Trinkets on our blog. - Elliott CEO, Trinket @hauspoor <https://via.intercom.io/c?url=http%3A%2F%2Ftwitter.com%2Fhauspoor&h=e06a625…> (919) 308-6681 <https://via.intercom.io/c?url=http%3A%2F%2Ftrinket.io&h=dedc0a69cb6c194c5e2…> *elliott(a)trinket.io <elliott(a)trinket.io>* from trinket.io 17 Oct 2014 Powered by Intercom <http://www.intercom.io/> Unsubscribe from our emails <https://app.intercom.io/unsubscribe?app_id=eezvdz15&conversation_id=5583787…> -- 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] Edu-sig Digest, Vol 135, Issue 4
by Marianne McKenna 21 Oct '14

21 Oct '14

I am out of the office, today., October 21st I will try to respond to email as I am able. If you need immediate help, please contact tech support.

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