Mailman 3 March 2016 - 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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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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Interactive Coding Web Pages?
by Peter Farrell 30 Mar '16

30 Mar '16

Hello to the Group! I'm redesigning my math-using-Python-programming course and need your input. I'd like to have the participants enter their code on a site like they do at CodingBat or CodeWars: the site tests the code and immediately gives the user feedback. Has anybody done this? Is there a template available for doing this, or is it a custom job? Is there an easier way, using an online IDE where teachers can set up classes? Would you recommend going with IPython/Jupyter notebooks instead? Any input you have would be appreciated. Thank you! Peter Farrell farrellpolymath.com hackingmathclass.blogspot.com

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remembering Python...
by kirby urner 26 Mar '16

26 Mar '16

Here's the somewhat nostalgically named "Remembering Python": https://youtu.be/6xQxhD29Rdc (a short Youtube for Python teachers) Twas from a last session (ten of ten) looking back on what we'd covered. I'm not excerpting this recording verbatim from the class. Rather, I'm going over some of what I've learned as a mentor, about ways to share Python. There's a Jupyter Notebook to go along: http://nbviewer.jupyter.org/github/4dsolutions/Python5/blob/master/Remember… Not that much to it, content-wise (it's short). In the Notebook and in the class notes (see "whiteboard") I hint at another "deep well": the special names. __invert__ in this case. I use it for encrypt / decrypt (permutations). I call these __ribs__ or "scaffolding" for use "backstage" in my banter. Learning Python involves learning this given special names. I notice in my two test browsers, the output of dir(__builtins__) gets truncated, chopped off, in the cited Notebook. Rendering directly on Github does not have this problem: https://github.com/4dsolutions/Python5/blob/master/Remembering1.ipynb On another topic, I attended the most recent Python User Group and followed up with this listserv posting: https://mail.python.org/pipermail/portland/2016-March/001744.html (talks about the user group towards the end and leads to more links). Kirby

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Pi Day / Jupyter NBs: new Youtube
by kirby urner 22 Mar '16

22 Mar '16

My newest Youtube on Jupyter Notebooks, Pi Day theme: https://youtu.be/x61uUu_amDk I just got Camtasia for Mac and this was my first project using it. Kirby

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some real teaching code I use with my code school students
by kirby urner 20 Mar '16

20 Mar '16

Here's some code I used with students last Monday, in Session 8 of 10. They've covered all the Python keywords as of Session 7 but we still need to keep going over all we've learned, seeing how the concepts mesh together. Actually at this point we haven't looked at the newest keywords async and await, nor yield from as a construct. An epiphany or at least a glue-it-together moment is when we show how a decorator of a function generator may be used to give a context manager. The two versions of the game below work the same way, but the second applies said decorator logic. The script suggests seeing the "context" as a Spooky Castle one enters, there to guess one of the keywords. That's the challenge. Guessing right still results in an exception being raised, but one that's handled by __exit__, whereas failure to "get it right" results in a different exception still in need of handling even after the scope of the with block. Kirby ==== # -*- coding: utf-8 -*- """ Created on Thu Feb 11 04:58:14 2016 @author: Kirby Urner Copyleft MIT License >From the docs: sys.exc_info() This function returns a tuple of three values that give information about the exception that is currently being handled. The information returned is specific both to the current thread and to the current stack frame.... see docs for more """ from keyword import kwlist from random import choice import sys class EscapeVictorious(Exception): pass class KickFromCastle(Exception): pass class Castle: def __init__(self, secret): self.__xyjk = secret self.guesses = 0 self.hints = 0 def __enter__(self): """get the ball rolling""" print("Welcome to Spooky Castle. To Escape, guess the secret keyword") return self # <-- make instance available within scope via 'as' def hint(self): if self.hints == 0: print("The keyword begins with", self.__xyjk[0]) elif self.hints == 1: print("The keyword is", len(self.__xyjk), "letters long.") else: print("You've had your two hints, sorry") self.hints += 1 def query(self): """gradations""" print("So what is the secret keyword then? Guess so far:", self.guesses) ans = input("You may answer (or type 'hint'): ") if ans == self.__xyjk: print("Excellent, we're done here") print("You have won the Copper Key") # <-- RealPlayer One (novel) raise EscapeVictorious("Copper Key") elif self.guesses == 5: print("Uh oh, you're out of guesses, sigh") raise KickFromCastle("We're done!") elif ans == "hint": self.hint() return else: self.guesses += 1 print("No, that's not it.") def __exit__(self, *exception_data): """raise a ruckus""" if exception_data[0] == EscapeVictorious: print("Congratulations!") print("Here is your", exception_data[1]) return True if exception_data[0] == KickFromCastle: print("Better Luck Next Time") print("The keyword was", self.__xyjk) return False if __name__ == "__main__": the_secret = choice(kwlist) try: with Castle(the_secret) as spooky: while True: spooky.query() except: print("Handling: ", sys.exc_info()[0].__name__) print(sys.exc_info()[1]) # <--- triggers __str__ print(type(sys.exc_info()[1])) === # -*- coding: utf-8 -*- """ Created on Thu Feb 11 06:00:49 2016 @author: Kirby Urner Copyleft MIT License """ from contextlib import contextmanager from keyword import kwlist from random import choice import sys class EscapeVictorious(Exception): pass class KickFromCastle(Exception): pass @contextmanager def Castle(secret): try: obj = Game(secret) print("Welcome to Spooky Castle. To Escape, guess the secret keyword") yield obj # <-- make instance available within scope via 'as' except EscapeVictorious as ex: print("Congratulations!") print("Here is your", ex) return None # default, could leave out or pass except KickFromCastle: print("Better Luck Next Time") print("The keyword was", obj._Game__xyjk) raise class Game: def __init__(self, the_secret): self.__xyjk = the_secret self.guesses = 0 self.hints = 0 def hint(self): if self.hints == 0: print("The keyword begins with", self.__xyjk[0]) elif self.hints == 1: print("The keyword is", len(self.__xyjk), "letters long.") else: print("You've had your two hints, sorry") self.hints += 1 def query(self): """gradations""" print("So what is the secret keyword then? Guess so far:", self.guesses) ans = input("You may answer (or type 'hint'): ") if ans == self.__xyjk: print("Excellent, we're done here") print("You have won the Copper Key") # <-- RealPlayer One (novel) raise EscapeVictorious("Copper Key") elif self.guesses == 5: print("Uh oh, you're out of guesses, sigh") raise KickFromCastle("We're done!") elif ans == "hint": self.hint() return else: self.guesses += 1 print("No, that's not it.") if __name__ == "__main__": the_secret = choice(kwlist) try: with Castle(the_secret) as spooky: while True: spooky.query() except KickFromCastle: print("Handling: ", sys.exc_info()[0].__name__) print(sys.exc_info()[1]) # <--- triggers __str__ print(type(sys.exc_info()[1]))

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welcome to algebra city!
by kirby urner 17 Mar '16

17 Mar '16

One of my mainstays, when it comes to teaching Python, is the Composable class. I worked on this Python type with Steve Holden back in the day, when he was writing his four part Python curriculum for O'Reilly School of Technology. His version of Composable shows up in Chapter One of the fourth course: http://archive.oreilly.com/oreillyschool/courses/Python4/Python4-01.html#s_… My current version of the Composer class, used as recently as last night in my Session 8-of-10 for Saisoft.net, is embedded in this Jupyter Notebook, which should render in any browser: http://nbviewer.jupyter.org/github/4dsolutions/Python5/blob/master/Composin… The usefulness of the Composer class is multifaceted: * It demonstrates operator overloading, providing meaning / behavior for both __mul__ and __pow__. * Algebraically, composition is a basic operation and relates to "piping" in the bash shell. Composing functions is core to lambda calculus. [1] When the output of a first function becomes the input to a next, that's composition. Example: $ ls *.py | wc -l which outputs the number of Python source code modules in a given directory. Notice how the pipe operator is used to get output from the command on the left to the command on the right. * Finally, Composable is usable as a class decorator, turning the decorated function into a composable one. So introducing composition of functions is an excuse to learn / reinforce many Python concepts. Kirby [1] per previous posts, whereas lambda calc is a highly specialized subject, if repurposed to contrast with delta calc i.e. conventional calculus, it becomes a marketing / publishing term for the kind of discrete math / compsci that states are starting to mandate. As a high schooler taking algebra, you might want to continue with more lambda than delta calc, depending on career plans.

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Re: [Edu-sig] Edu-sig Digest, Vol 152, Issue 11
by Peter Farrell 16 Mar '16

16 Mar '16

Hi, KIrby, Love the IPython notebook. Great idea to create a notebook with all the Pi stuff, including the funny video. Peter On Tue, Mar 15, 2016 at 9:00 AM, <edu-sig-request(a)python.org> wrote: > Send Edu-sig mailing list submissions to > edu-sig(a)python.org > > To subscribe or unsubscribe via the World Wide Web, visit > https://mail.python.org/mailman/listinfo/edu-sig > or, via email, send a message with subject or body 'help' to > edu-sig-request(a)python.org > > You can reach the person managing the list at > edu-sig-owner(a)python.org > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Edu-sig digest..." > > > Today's Topics: > > 1. another code school tool ( + other topics) (kirby urner) > 2. Pi Day Fun (3.14, 2016) (kirby urner) > 3. Re: Pi Day Fun (3.14, 2016) (Matt Harrison) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Mon, 14 Mar 2016 11:25:46 -0700 > From: kirby urner <kirby.urner(a)gmail.com> > To: "edu-sig(a)python.org" <edu-sig(a)python.org> > Subject: [Edu-sig] another code school tool ( + other topics) > Message-ID: > < > CAPJgG3Q4aAkSkcsCFYfpsa1bAf5fou-xKcyEQmO0oXsspHXybQ(a)mail.gmail.com> > Content-Type: text/plain; charset="utf-8" > > *COOL TOOL*: > > Another tool I've been meaning to mention, apropos of recent threads: > > http://www.freecodecamp.com/ > > I signed up for it wearing my PDX Code Guild hat [1], interested in "the > competition" but then I'd say FreeCodeCamp is operating in a different > ballpark, too distant from ours to be considered a direct competitor in our > market (we do in-person boot camps). > > FreeCodeCamp gives you thousands of DIY exercises across the several "full > stack" topics, but also promotes Chat and Meetup modes, so yes, you'll > actually start interacting with and maybe meeting some of your fellow > trainees if you show initiative (self-filtering). Granted, some folks are > too remote to easily join in-person meetups; urban lifestyles are more > conducive to that mode. > > As one climbs the ladder (I got off it for now, can't climb into every > treehouse) the projects get more complex and this morning my Chatter Box is > filled with talk of Cloud9 (apropos), where apparently they do deployment > exercises. > > *CODE SCHOOL CONSULTING*: > > On another front, I'm very "not pushy" about Python, meaning in this > context that if Vietnam code schools I'm advising prefer a MEAN stack (know > what that is? I do), then more power to 'em. [2] > > Far be it from me to say a pure JavaScript stack should be written off as > 2nd class. These are spanking new technologies and we want willing guinea > pigs to dive and and use them -- to their own advantage. > > The theory is: if you learn how to learn then the tool chain you pick will > stay variable, given new tools are coming in, yielding opportunities worth > availing of. > > So by all means, start with a MEAN stack and migrate to something else over > time as you learn new tricks (there're always new ones to learn); just pick > an entry point that works, includes a winning hand possibility, then maybe > shuffle the deck and play a different hand (e.g. switch to something more > Pythonic). > > *LISTOWNER BUSINESS*: > > if you dig into admin details you'll see I've made > urner(a)alumni.princeton.edu a listowner however this may not prove optimum > in the long run so don't be surprised if I switch back to my kirby.urner > address at Gmail. > > I've also posted from my work address with O'Reilly during the chapter when > O'Reilly experimented with running a code school (oreillyschool.com), > since > closed. > > Just helping document my activity, a geek thing to do. > > I can't recall if I've posted from any other email addresses over the > years. I go way back on edu-sig, but have only recently assumed any > listowner duties. > > Fortunately Naomi Ceder is co-piloting as listowner and has considerable > experience (compared to me), listowning within Python.org, using Mailman in > particular. > > *YAY MAILMAN*: > > I really like Mailman and am recommending it to at least one of my geek > subcultures (one fairly new to the listserv concept in general -- yes, > behind the times, stuck in 1790s mostly :-D). > > Finding a service that lets us set up like what Python.org has, a set of > Mailman listservs used for self-governance, is on my list of Things to Do > in a role-playing -- or we say "hat wearing" -- capacity (@npym_it). > > Happy Pi Day! > > Kirby > > [1] http://mean.io/#!/ > M: MongoDB > E: Express.js > A: Angular.js > N: Node.js > > Funny: > http://xkcd.com/1655/ >

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Pi Day Fun (3.14, 2016)
by kirby urner 14 Mar '16

14 Mar '16

http://nbviewer.jupyter.org/github/4dsolutions/Python5/blob/master/Pi%20Day… The above URL renders a Github-saved public I-Python Notebook using nbviewer, a utility for rendering any Jupyter notebook with a public URL. My example Python code is generator-centric as successive approximations of something, approaching a limit, lends itself to such yield-based treatment. Kirby

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another code school tool ( + other topics)
by kirby urner 14 Mar '16

14 Mar '16

*COOL TOOL*: Another tool I've been meaning to mention, apropos of recent threads: http://www.freecodecamp.com/ I signed up for it wearing my PDX Code Guild hat [1], interested in "the competition" but then I'd say FreeCodeCamp is operating in a different ballpark, too distant from ours to be considered a direct competitor in our market (we do in-person boot camps). FreeCodeCamp gives you thousands of DIY exercises across the several "full stack" topics, but also promotes Chat and Meetup modes, so yes, you'll actually start interacting with and maybe meeting some of your fellow trainees if you show initiative (self-filtering). Granted, some folks are too remote to easily join in-person meetups; urban lifestyles are more conducive to that mode. As one climbs the ladder (I got off it for now, can't climb into every treehouse) the projects get more complex and this morning my Chatter Box is filled with talk of Cloud9 (apropos), where apparently they do deployment exercises. *CODE SCHOOL CONSULTING*: On another front, I'm very "not pushy" about Python, meaning in this context that if Vietnam code schools I'm advising prefer a MEAN stack (know what that is? I do), then more power to 'em. [2] Far be it from me to say a pure JavaScript stack should be written off as 2nd class. These are spanking new technologies and we want willing guinea pigs to dive and and use them -- to their own advantage. The theory is: if you learn how to learn then the tool chain you pick will stay variable, given new tools are coming in, yielding opportunities worth availing of. So by all means, start with a MEAN stack and migrate to something else over time as you learn new tricks (there're always new ones to learn); just pick an entry point that works, includes a winning hand possibility, then maybe shuffle the deck and play a different hand (e.g. switch to something more Pythonic). *LISTOWNER BUSINESS*: if you dig into admin details you'll see I've made urner(a)alumni.princeton.edu a listowner however this may not prove optimum in the long run so don't be surprised if I switch back to my kirby.urner address at Gmail. I've also posted from my work address with O'Reilly during the chapter when O'Reilly experimented with running a code school (oreillyschool.com), since closed. Just helping document my activity, a geek thing to do. I can't recall if I've posted from any other email addresses over the years. I go way back on edu-sig, but have only recently assumed any listowner duties. Fortunately Naomi Ceder is co-piloting as listowner and has considerable experience (compared to me), listowning within Python.org, using Mailman in particular. *YAY MAILMAN*: I really like Mailman and am recommending it to at least one of my geek subcultures (one fairly new to the listserv concept in general -- yes, behind the times, stuck in 1790s mostly :-D). Finding a service that lets us set up like what Python.org has, a set of Mailman listservs used for self-governance, is on my list of Things to Do in a role-playing -- or we say "hat wearing" -- capacity (@npym_it). Happy Pi Day! Kirby [1] http://mean.io/#!/ M: MongoDB E: Express.js A: Angular.js N: Node.js Funny: http://xkcd.com/1655/

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