Mailman 3 March 2013 - 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] RurPLE-NG is nice
by Jurgis Pralgauskis 05 Apr '14

05 Apr '14

Some updates: - separated Variables Watch and Output panes, to be seen simultaneusly - implemented Breakpoints :) - beta style Todo: - let enter arbitrary watch expressions http://ftp.akl.lt/users/jurgis/python/rurple-NG053.png http://ftp.akl.lt/users/jurgis/python/rurple-ng-dz0-SplitLogVars_and_Breakp… for windows one doesn't need to install python separately, just unzip and run :) http://ftp.akl.lt/users/jurgis/python/RURPLE-NG-0.53%20%5bindependent%20exe… ps.: RurPLE-NG uses py3 unicode_literals, with_statement, division, print_function so code is generally py3 compliant. when wxpy will work well with py3 it shouldn't be too hard to port fully... >> >> just wanted to mention, >> that http://dev.lshift.net/paul/rurple/ >> is a very nice and lightweit PLE. >> >> what I like most (compared to RurPLE) are: >> 1) variables watch list (if it had breakpoints, it would rock :)

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Easy Web Environment to post pupils Python Creations
by Philip Bagge 01 Apr '14

01 Apr '14

Dear Colleagues, My Y6 pupils (10-11 year olds) have been creating some simple text based linear adventures using Python. Does anyone know of a way we can play their adventures online? They are not very complicated. You can see the planning here. https://sites.google.com/site/pythoncodecouk/python-adventure Also as a new person to your forum does anyone know of an easy way to search you archives just in case someone has already answered this question. Thanks in advance for any help Phil Bagge -- Primary ICT Advanced Skills Teacher HCC Teacher & IT Manager http://code-it.co.uk

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Python MOOC (massive open online course)
by John Posner 10 Jun '13

10 Jun '13

At the nytimes.com site, I came across a reference to this Python course in the comments to Thomas Friedman's latest column: http://blog.topfreeclasses.com/2012/12/an-introduction-to-interactive-pytho… Does anyone have any direct knowledge of this (or any other) Python MOOC? -John

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online coding?
by Karine Laidley 26 Mar '13

26 Mar '13

Dear Python users, I wanted to check with you if you know of a good site that allows students to submit Python code to be checked for correctness. I know there is a codebat site but I found it limited in what it offers. Ideally, I want to offer students problems to solve from simple print statements, to calculations, to formatting, to conditionals and repetitions... even better, if we can actually create our own problem sets and solutions to be checked against, that would be amazing. Any thoughts? Thank you, Karine Laidley Computer Science Teacher (6th and 7th grade) AMSA Charter School Marlborough, MA (508)597-2400 k.laidley(a)amsacs.org

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Re: [Edu-sig] online coding?
by Karine Laidley 20 Mar '13

20 Mar '13

I want to thank everyone for their responses. I will look into the options and see which might get me closest to what I need... As for the browser option for Python, all will be useful. I have a few students who do not have computers at home or limited space... Thanks again. Karine Laidley Computer Science Teacher (6th and 7th grade) AMSA Charter School Marlborough, MA (508)597-2400 k.laidley(a)amsacs.org From: Karine Laidley Sent: Tuesday, March 19, 2013 9:18 PM To: 'edu-sig(a)python.org' Subject: online coding? Dear Python users, I wanted to check with you if you know of a good site that allows students to submit Python code to be checked for correctness. I know there is a codebat site but I found it limited in what it offers. Ideally, I want to offer students problems to solve from simple print statements, to calculations, to formatting, to conditionals and repetitions... even better, if we can actually create our own problem sets and solutions to be checked against, that would be amazing. Any thoughts? Thank you, Karine Laidley Computer Science Teacher (6th and 7th grade) AMSA Charter School Marlborough, MA (508)597-2400 k.laidley(a)amsacs.org

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Big thanks to Naomi Ceder for putting together the EDU Summit!
by Jeff Elkner 20 Mar '13

20 Mar '13

We all owe a big thank you to Naomi Ceder for all the work she put in organizing the EDU Summit. After spending years at Pycons meeting with the between 5 and 10 people at the conference interested in Python in Education over a dinner, it was exciting indeed to see 90+ people this year. Thanks, Naomi! jeff elkner

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Python at the University of São Paulo
by Jeff Elkner 19 Mar '13

19 Mar '13

Luciano Ramalho stopped by at the Pycon sprint to tell me that the University of São Paulo (http://en.wikipedia.org/wiki/University_of_S%C3%A3o_Paulo) recently adopted Python in its Introductory CS program. I told him I would pass this good news along to the edu-sig, and invited him to join us on this list. jeff elkner

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Python Epistemology
by michel paul 19 Mar '13

19 Mar '13

This was the title of a 5-minute 'lightening talk' by Allen Downey, author of Think Python <http://www.greenteapress.com/thinkpython/html/index.html>, during the educational summit here at PyCon. Main points: * - Nat ural L ang uage : expressive and readable, but verbose and imprecise. - Math ematical notation : concise and precise, but not readable or executable. - M ost programming languages: precise and executable, but verbose and not readable. Hmmm ... can anyone think of an expressive, readable, concise, precise, and executable symbolic language? : ) He went on to show a traditional mathematical formula representing Bayesian inference and compared it to the corresponding Python code. The Python code was similar to natural language and represented a flow of ideas. It was comprehensible. His point was that we often think we need to first express our ideas in traditional mathematical notation and then translate the math into executable code. But his point was no, we can code our ideas directly. It is a new kind of mathematical expression. I was so delighted to hear this, as these are the conclusions I have come to as well. It's absolutely true that coding reflectively helps clarify one's ideas, and this is why it belongs in education. I've repeatedly had the experience that coding something I had long taken for granted in math got me to see it in a new light. I've come to view traditional math syntax as a kind of clever shorthand we developed before we had computers. I think the traditional syntax creates a kind of cognitive illusion in students and teachers that that's 'really' the math. And then throwing calculators into the mix just solidifies the illusion. Everyone in K-12, students and teachers, thinks that the math is 'really' on a piece of paper, in traditional notation, and that the technology is something on the side we turn to in order to help us get the math onto the paper when the calculations get too tough. I think that picture is flawed and antiquated. The technology itself is the new paper. Computational languages are the new algebra. * PyCon was amazing. It was my first one. Very inspiring. Time definitely well spent. -- Michel =================================== "What I cannot create, I do not understand." - Richard Feynman =================================== "Computer science is the new mathematics." - Dr. Christos Papadimitriou ===================================

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Re: [Edu-sig] Edu-sig Digest, Vol 116, Issue 4
by Jeff Elkner 17 Mar '13

17 Mar '13

Lee, if you are looking for a classroom teacher to try out pyguin in the classroom, sign me up! I'll have it installed in my lab on Thursday, when I return, in any case. It rocks! Now a question: how difficult would it be to get pyguin to output svg images? Jeff Elkner On Sun, Mar 17, 2013 at 1:07 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 > http://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. [ANNC] pynguin-0.13 python turtle graphics application now > uses python 3 (Lee Harr) > 2. Python Epistemology (michel paul) > 3. Re: Python Epistemology (Kirby Urner) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Sun, 17 Mar 2013 04:42:59 +0430 > From: Lee Harr <missive(a)hotmail.com> > To: "python-list(a)python.org" <python-list(a)python.org>, > "edu-sig(a)python.org" <edu-sig(a)python.org> > Subject: [Edu-sig] [ANNC] pynguin-0.13 python turtle graphics > application now uses python 3 > Message-ID: <BLU168-W96F128EFCAA20324B9E710B1EF0(a)phx.gbl> > Content-Type: text/plain; charset="windows-1256" > > > Pynguin is a python-based turtle graphics application. > ??? It combines an editor, interactive interpreter, and > ??? graphics display area. > > It is meant to be an easy environment for introducing > ??? some programming concepts to beginning programmers. > > > http://pynguin.googlecode.com/ > > > This release ports Pynguin to Python 3. > > > Pynguin is tested with Python 3.2.3 and PyQt 4.9.3 and > ??? will use Pygments syntax highlighting if available. > > Pynguin is released under GPLv3. > > > Changes in pynguin-0.13: > ??? Now uses (requires) Python 3 > ??????? - Tested with Python 3.2.3 > > ??? Important fixes > ??????? - New approach for threading of user code > ??????????? - should provide safer, more reliable, termination of user code > ??????????? - can now reliably stop code like ... while 1: pass > ??????? - Preserves fill state and color when changing avatar > > ??? Other fixes > ??????? - Preserves name label when changing avatar > ??????? - Tries harder to go as fast as possible for "instant" setting > ??????????? - throttles back on CPU when not running user code > > ??? Pynguin API > ??????? - Logo-mode coordinates and angles now available > ??????????? - Switch mode using Pynguin -> Mode -> Logo > ??????????? - or create new instance with mlogo=ModeLogo() > ??????? - Python turtle-mode coordinates and angles now available > ??????????? - Switch mode using Pynguin -> Mode -> Turtle > ??????????? - or create new instance with mturtle=ModeTurtle() > ??????? - xy(x, y) re-uses goto(x, y) code > ??????? - xyh() uses xy() and h() to retrieve values > ??????? - color() takes an optional alpha channel value for transparency > ??????????? - color('ralpha') chooses a random color with random alpha > ??????? - Each pynguin's speed can now be set individually > > ??? Canvas > ??????? - Added a dialog for pen, background, and fill default colors > ??????????? - sets these colors on program startup > ??????????? - uses these colors for reset() > ??????????? - also used when adding new pynguins > ??????? - Can now track any pynguin > ??????? - Can zoom to fit entire drawing > > ??? UI > ??????? - Added new Pynguin menu for avatar and mode selection > ??????? - Added alpha value selector to pen and fill color dialogs > > ??? Integrated Editor > > ??? Integrated Console > > ??? Examples > ??????? - All ported to Python 3 > ??????? - Added examples using colors with alpha channel values > ??????? - Added finish line to horserace > > > > > ------------------------------ > > Message: 2 > Date: Sat, 16 Mar 2013 20:14:33 -0700 > From: michel paul <pythonic.math(a)gmail.com> > To: edu-sig(a)python.org > Subject: [Edu-sig] Python Epistemology > Message-ID: > <CANuze1+1-34XASccBaiDis_Kpty=r7nhZVqwKa6UnFzpC1Xt6A(a)mail.gmail.com> > Content-Type: text/plain; charset="iso-8859-1" > > This was the title of a 5-minute 'lightening talk' by Allen Downey, author > of Think Python > <http://www.greenteapress.com/thinkpython/html/index.html>, during > the educational summit here at PyCon. Main points: > > * > > - Nat > ural L > ang > uage > : expressive and readable, but verbose and imprecise. > - Math > ematical notation > : concise and precise, but not readable or executable. > - M > ost > programming languages: precise and executable, but verbose and not > readable. > > > Hmmm ... can anyone think of an expressive, readable, concise, precise, and > executable symbolic language? : ) > > He went on to show a traditional mathematical formula representing Bayesian > inference and compared it to the corresponding Python code. The Python code > was similar to natural language and represented a flow of ideas. It was > comprehensible. His point was that we often think we need to first express > our ideas in traditional mathematical notation and then translate the math > into executable code. But his point was no, we can code our ideas directly. > It is a new kind of mathematical expression. > > I was so delighted to hear this, as these are the conclusions I have come > to as well. It's absolutely true that coding reflectively helps clarify > one's ideas, and this is why it belongs in education. I've repeatedly had > the experience that coding something I had long taken for granted in math > got me to see it in a new light. I've come to view traditional math syntax > as a kind of clever shorthand we developed before we had computers. I think > the traditional syntax creates a kind of cognitive illusion in students and > teachers that that's 'really' the math. > And then throwing calculators into the mix just solidifies the illusion. > Everyone in K-12, students and teachers, thinks that the math is 'really' > on a piece of paper, in traditional notation, and that the technology is > something on the side we turn to in order to help us get the math onto the > paper when the calculations get too tough. I think that picture is flawed > and antiquated. The technology itself is the new paper. Computational > languages are the new algebra. > * > > PyCon was amazing. It was my first one. Very inspiring. Time definitely > well spent. > > -- > Michel > > =================================== > "What I cannot create, I do not understand." > > - Richard Feynman > =================================== > "Computer science is the new mathematics." > > - Dr. Christos Papadimitriou > =================================== >

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