Mailman 3 May 2012 - 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

xturtle online via processing.js !?
by Jurgis Pralgauskis Sept. 27, 2012

Sept. 27, 2012

Hi, I am struggling around with interactive online py tutorials with https://launchpad.net/projects/intro-to-code (ith might become securely sandboxed soon, as pypy made it possible http://blog.sandbox.lt/en/WSGI%20and%20PyPy%20sandbox :) but one more thing is I'd like to let access xturtle functionality online - one possible way could be triggering tkinter to save its canvas to ps, and then convert them with imagemagic and show via web (animated gif or static) - but if pyjamas can render GUI for js (http://www.google.lt/search?&q=pyjamas+python ), mayby there is a way to **translate turtle commands to processing.js analogues** http://ejohn.org/blog/processingjs/ would it be difficult -- how do you think? -- Jurgis Pralgauskis tel: 8-616 77613; jabber: jurgis(a)akl.lt; skype: dz0rdzas; Don't worry, be happy and make things better ;) http://sagemath.visiems.lt

4 6

Python in middle school redux
by mary.dooms＠comcast.net May 30, 2012

May 30, 2012

I am interesting in gaining your feedback on these Python programming lessons, particularly ones that address the 6th and 7th grade Common Core. http://www.google.com/edu/computational-thinking/lessons.html I had good intentions of using python with my 6th graders, however a lack of both time and vision have prevented me from doing so. What intrigues me about these lessons is that they use programming to solve problems--deconstruct the problem to construct an algorithm. The lessons are very focused which make the task of writing a program manageable. A webinar featuring Phil Wagner will air June 6. http://mathfuture.wikispaces.com/ExploringComputationalThinking What are your thoughts? Is the another database of python lessons that address the Common Core?

1 0

visualizing namespaces
by kirby urner May 30, 2012

May 30, 2012

Steve Holden was asking on the PSF members list (some overlap with here) for other ways to diagram / teach about namespaces in his slides. This is the slide show he's talking about. http://holdenweb.com/files/PythonIntro.pdf (namespaces = like clouds) After some back and forth, another visual: http://www.flickr.com/photos/17157315@N00/7276024654/in/photostream The namespace is a way objects on the heap get to be "thought of" by the interpreter. The "thought balloon" (similar to Steve's cloud) in contrast to a pile of rocks (objects) belongs to the Python inside. Kirby

1 1

Re: [Edu-sig] Teaching python at a Computer Clubhouse
by Laura Creighton May 22, 2012

May 22, 2012

In a message of Tue, 22 May 2012 08:54:47 +1200, Carl Cerecke writes: >I'm thinking of becoming a mentor at a local Computer Clubhouse >http://www.computerclubhouse.org/. In particular, there are some kids the >re >who are quite keen to learn to make their own games, but none of the >current mentors know any programming (one said that he had done some >"programming" in HTML). >I would be grateful for any recommendations for material to help me and t >he >kids. I have plenty of programming experience and some teaching experienc >e >(at the university level, though). I've written some text-only turn-based >games in python before (about the level of connect-4), but nothing with >graphics. The idea is supposed to be that this is driven by the interests >of the children, but I need to balance that with the requirement for a bi >t >of a programming foundation as well if they're going to be successful in >writing the sort of games they're interested in. I also think I need to >make sure their expectations are realistic... >So, any advice/recommendations? > >Cheers, >Carl. How old are the members of the clubhouse? If at all possible you should let kids group by interest. Date of manufacture (birth date) is a rotten way to sort people and your kids, like everybody else, will be happier if people are sorted by something other than 'birth date'. I steal regularly from http://www.briggs.net.nz/snake-wrangling-for-kids.html and given that the author is in NZ as well, he might have some insights that are better shared in person. best of appreciation for what you are doing, Laura Creighton

3 2

Teaching python at a Computer Clubhouse
by Carl Cerecke May 21, 2012

May 21, 2012

I'm thinking of becoming a mentor at a local Computer Clubhouse http://www.computerclubhouse.org/. In particular, there are some kids there who are quite keen to learn to make their own games, but none of the current mentors know any programming (one said that he had done some "programming" in HTML). I would be grateful for any recommendations for material to help me and the kids. I have plenty of programming experience and some teaching experience (at the university level, though). I've written some text-only turn-based games in python before (about the level of connect-4), but nothing with graphics. The idea is supposed to be that this is driven by the interests of the children, but I need to balance that with the requirement for a bit of a programming foundation as well if they're going to be successful in writing the sort of games they're interested in. I also think I need to make sure their expectations are realistic... So, any advice/recommendations? Cheers, Carl.

3 2

Re: [Edu-sig] Online Data Base of Dynamic Question
by Laura Creighton May 21, 2012

May 21, 2012

In a message of Mon, 21 May 2012 13:08:10 -0300, Raniere Gaia Silva writes: >Hi, > >I was searching for a easily and quickly way to make math tests/exercises >(I don't want a course management system like moodle <http://moodle.org/> > or >webwork <http://webwork.maa.org/>). >Since I didn't find any great solution I start to make one: >http://smart-teacher.alwaysdata.net/ > >would be interested in comments :) >and in which other groups I could discuss it? > >Raniere I have taken the liberty of posting this to testing-in-python. Many testing frameworks already exist, and some of them -- Geoff Bache's TextTest comes to mind -- may work to do what you want with minimal tweaking. But you will need to describe what it is that you want to do. Mostly we test python code here, but some of us have things that deal with more arbitrary input. And there is also Crunchy Frog which might be adaptable. Around here (TIP) we like use cases lots more than we like discussion of the internal vision for the project, which means in describing what you want, if you can say things like 'I want the teacher to provide X, and when the student provides Q, the result Z is generated' we will have an easier time of seeing if the frameworks we know and maintain can be of use to you. There are dozens represented here, all quite friendly -- so you will not be able to narrow down your choice by asking 'which is the best'. The answer is always 'for whom? to do what?'. But I think customising something here will be a lot easier than writing your own from scratch, especially if you have never done this before. And even if our solutiuons are overkill for your problems -- well, you will at least get to meet a nice group of people, many of whom have also felt the itch to write their own frameworks, and who can talk about some of the problems that await you. best, Laura

1 0

Online Data Base of Dynamic Question
by Raniere Gaia Silva May 21, 2012

May 21, 2012

Hi, I was searching for a easily and quickly way to make math tests/exercises (I don't want a course management system like moodle <http://moodle.org/> or webwork <http://webwork.maa.org/>). Since I didn't find any great solution I start to make one: http://smart-teacher.alwaysdata.net/ would be interested in comments :) and in which other groups I could discuss it? Raniere

2 1

Next Steps in Python, for teachers
by Alan O'Donohoe May 20, 2012

May 20, 2012

We held a Python event for 39 teachers new to Python at our school this week. You might find the blog post with photos of interest. http://teachcomputing.wordpress.com/2012/05/18/cas-hub-next-steps-in-python/ Alan Mr A O'Donohoe Principal Teacher of ICT, Our Lady's High School, Preston, UK Twitter @teknoteacher, Skype alan.o.donohoe , Blog http://teachcomputing.wordpress.com/

3 2

edu-sig in Pythonia
by kirby urner May 4, 2012

May 4, 2012

A few of us at Pycon were nodding heads (+1ing) over the idea that our subculture / ethnicity could evolve these "canned talks" that different people deliver in their personalized style. More than that, they demonstrate new "teaching techniques" such that the audience might appreciate how advances in pedagogy -- and in andragogy -- still occur. Consider the O'Reilly 'Head First Into...' series. Like 'for Dummies', it explains up front that there's psychology at work, smart cookies have baked a new mix of graphic art, sound bites, who knows what's coming, and you, the reader / student are in for a treat. But then books, like videos, are a somewhat passive medium. Once you jump on that gym equipment, that treadmill, that weight pump, you know there's more to the educational experience than having your butt in a chair. Among the canned topics would be ArgsKwargs. Everyone learning Python needs to keep spiraling through the ArgsKwargs literature, wherein we do what in other languages might be called gathering and scattering. The star and double star, which C-language readers are used to seeing anyway in function headers etc., have become scavengers, accepting / liberal "all may pass" type guards at the gate (function entrance), and yet still there are rules (positionals before keyword). Used when passing arguments, the star and double-star are "exploders" (scatterers), setting free their tuples and dicts to mingle as individuals. >>> def baby(skin="soft", noise_might_be = "crying", **blahblah): print ("Hey baby, I notice the {} skin, and the {} noise you're making".format(skin, noise_might_be)) print(blahblah) >>> random_keys = {"safe":"12-15-44", "skin":"purple", "tomorrow":"wash car"} >>> baby(**random_keys) Hey baby, I notice the purple skin, and the crying noise you're making {'safe': '12-15-44', 'tomorrow': 'wash car'} Another canned talk -- could be lightning format -- is IterStuff, beginning with the difference between an iterator and an iterable, climbing through generators (with plenty of send use) to iterator defining classes, to itertools more generally, and a discussion of "just in time" versus pre-stocking memory with impossibly huge inventories. Here I'd suggest a lore-based approach wherein we go over how Python itself has become ever more fascinated with iterators. How is it that a range class object is a sequence (indexable) whereas the dict_items object is not (not indexable)? >>> dict(a=1,b=2).items()[0] Traceback (most recent call last): File "<pyshell#0>", line 1, in <module> dict(a=1,b=2).items()[0] TypeError: 'dict_items' object does not support indexing >>> range(2)[0] 0 Then there'd be the protocol talks i.e. lets talk about interfaces in the abstract. The iterator is our first example, in being about having __iter__ and __next__. Then comes the descriptor and its interface / protocol. The point being: we should always have these talks. There will always be people new to Python (in this model), or people wanting a refresher and (here's the kicker) people needing practice in their teaching techniques in front of an audience that's already very much in the ballpark (already at a Pycon, not just casually dropping by to see what this might be about). Also: the people most interested in teaching Python, such as here on edu-sig, should be most involved in organizing this track. The track of standard topics, things we all need to know -- but how best to share? That track and that question are one of our angles / self-chosen responsibilities, along with the poster session. I would extend this philosophy to say edu-sig types should also take some 3rd party modules under their collective wing, by which I mean to include such worthies as: Visual Python, I-Python, matplotlib, numpy, Blender and web frameworks (including Google App Engine). OK, now that's starting to sound like a complete Pycon, not just a track. Fair enough. The edu-sig "base" is around a track of core topics. Then each topic is conceived to "branch off" into various "worlds" or "namespaces". E.g the IterStuff branches off into Twisted and asynchronous techniques such as David Beazely has specialized in inventing and teaching. We'd need more diagrams, roadmaps, to show the "lay of the land" (Pythonia). Seeing it one way doesn't preclude also seeing it in other ways too. Kirby

4 4