Mailman 3 December 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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"Logical connectives Hasse diagram"
by Wes Turner 31 Dec '17

31 Dec '17

"Logical connectives Hasse diagram" I've been searching for this for my whole life! TIL this forms a "Rhombic dodecahedron" https://commons.wikimedia.org/wiki/File:Logical_connectives_Hasse_diagram.s… Happy New Year!

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the "best way" to teach Python
by kirby urner 28 Dec '17

28 Dec '17

https://medium.com/@kirbyurner/whats-the-best-way-to-teach-python-675d4bfbd… Recent essay on Medium. Kirby

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Excel losing out to open source?
by kirby urner 18 Dec '17

18 Dec '17

I know in my own Python classes I talk about the power of a pandas dataframe as like having a spreadsheet and a database object combined, in a container you get to program around, in Python. What in Office is like that? There's an shift away from spreadsheets as the cornerstone of data analysis perhaps? The JP Bader link goes to further discussion. Also check Chipy archives. Kirby Culling from Chipy (open archive): ---------- Forwarded message ---------- From: Jeremy McMillan <jeremy.mcmillan(a)gmail.com> Date: Thu, Dec 14, 2017 at 7:06 PM Subject: Re: [Chicago] Excel team considering Python as scripting language: asking for feedback To: The Chicago Python Users Group <chicago(a)python.org> This looks like Microsoft realizing they are losing to Jupyter Notebook and Pandas + Matpotlib. On Thu, Dec 14, 2017 at 4:38 PM, JP Bader <jp(a)zavteq.com> wrote: > http://hn.premii.com/#/comments/15927132 > > _______________________________________________ > Chicago mailing list > Chicago(a)python.org > https://mail.python.org/mailman/listinfo/chicago > >

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Re: [Edu-sig] Lost reference to an online Scratch-like Python environment
by Aivar Annamaa 17 Dec '17

17 Dec '17

Found it finally! :) It'swww.codesters.com <https://www.codesters.com/> Check it out: https://www.codesters.com/curriculum/intro-to-codesters/Building+your+First… best regards, Aivar On 16.12.2017 10:29, Michal Kaukic wrote: > Hi, Aivar, > >>> Couple of months ago I found a link to a browser-based Python >>> environment, which allowed constructing graphical Scratch-like >>> scenarios with Python code. There was a tutorial where you had to >>> make a fox move. > > maybe Blockly (https://developers.google.com/blockly/) > or Snap! (BYOB) (http://snap.berkeley.edu/)? > > Michal

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Lost reference to an online Scratch-like Python environment
by Aivar Annamaa 15 Dec '17

15 Dec '17

Hi! Couple of months ago I found a link to a browser-based Python environment, which allowed constructing graphical Scratch-like scenarios with Python code. There was a tutorial where you had to make a fox move. Unfortunately I've lost the address, forgot the name and can't find it by googling anymore. Does anyone recognize this environment? best regards, Aivar

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Re: [Edu-sig] thumbs up Socratia for Python teaching videos on Youtube
by Andrew Harrington 05 Dec '17

05 Dec '17

Cool, Kirby! Thanks. Dr. Andrew N. Harrington Computer Science Department Graduate Program Director gpd(a)cs.luc.edu Loyola University Chicago 207 Doyle Center, 1052 W Loyola Ave. http://www.cs.luc.edu/~anh Phone: 773-508-3569 Dept. Fax: 773-508-3739 aharrin(a)luc.edu (as professor, not gpd role) On Mon, Dec 4, 2017 at 4:58 PM, kirby urner <kirby.urner(a)gmail.com> wrote: > > From email (with attached invoice) to one of my clients (WorkingIT.com): > > > """ > > I'm still liking Socratia, here's a new one on text files: > > https://youtu.be/4mX0uPQFLDU (I left a positive comment) > > Good on using keyword 'with' when opening files, also on using > print(content, file = f) as an smart alternative. Bravo. > > Happy New Year! > > """ > > Happy New Year edu-sig. > > Kirby > > >

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thumbs up Socratia for Python teaching videos on Youtube
by kirby urner 04 Dec '17

04 Dec '17

>From email (with attached invoice) to one of my clients (WorkingIT.com): """ I'm still liking Socratia, here's a new one on text files: https://youtu.be/4mX0uPQFLDU (I left a positive comment) Good on using keyword 'with' when opening files, also on using print(content, file = f) as an smart alternative. Bravo. Happy New Year! """ Happy New Year edu-sig. Kirby

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