Mailman 3 August 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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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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high school "Pythonic math": Vector as pivotal (+ addendum on recent recipes)
by kirby urner 26 Aug '16

26 Aug '16

Per these paragraphs to a listserv for Physics teachers -- to which I was invited by one Dr. Bob Fuller, a former AAPT chairman -- I'm underlining a Vector type as one of the hallmarks of high school math: === [ posted about 2.5 hours ago ] === Your remarks on fluency are well taken. I'm just about to post something to edu-sig about the Vector class (class as in "type of object") and its pivotal role in grades 9-12 (as we say in this namespace). That'd be along both the delta and lambda tracks, continuous and discrete. Luciano Ramalho has recently published the book 'Fluent Python' which is appearing in several languages (I've met the guy a few times, been in his workshops or seen them on video). Luciano does a really fluent Vector type, as many dimensions as you want. With operator overloading, you can add them (v1 + v2), scale them (3 * v1), multiply them by matrices to get more vectors. You could say, when applying a rotation matrix, that "it's the same vector, just moved" but more disciplined functional programmers prefer immutable objects begetting new immutable objects, minimizing hidden (contained) state. Even with OO languages, there's something called programming in a more functional way. 'Functional Python' by Mertz is another popular title. The sympy library has a Clifford Algebra bivector submodule that I've not played with yet. === ... continuing that thought ... Once you have the bare bones model, the mathematical Vector, then you get to wire it up to different strategies for rendering. A simple and mathematically correct approach has all Vectors originating at the origin, pointing to points, such that the edges of a Polyhedron around said origin are each defined by two endpoint Vectors. e = Edge(v0, v1). Rendering edges, vertexes and faces (E, V, F) is a common theme, regardless of rendering back and, be that ray tracer, Pi3D or what have you. This was my approach in stickworks.py -- separate model from visualization code to some degree. I experimented with tighter and looser coupling. Like if you can interactively make graphics happen in a window, from a REPL in real time, so much the better. http://4dsolutions.net/ocn/python/stickworks.py (source) https://youtu.be/4iMSGKXJ_Ds (Youtube intro) A wrinkle in my curriculum writing is we may go on to re-implement the Vector concept using "quadray coordinates" (see Wikipedia) per this Jupyter notebook: ' http://nbviewer.jupyter.org/github/4dsolutions/Python5/blob/master/Polyhedr… ' I'm thinking lots of math teachers might like to go this route, not necessarily starting with my source code or anyone else's in particular (maybe Luciano's) as an exercise in learning / teaching pure Python. --------------------------------- Addendum re Raspberry Pi, as a polyhedrons rendering machine (the theme of my last two posts): I'm still working with Adrian Rossiter on OpenGL issues. His antiview runs but is not yet rendering properly https://flic.kr/p/KBCcqy (messed up antiview view in upper right) probably because Pi use OpenGL ES, not what he'd coded for? I may see a fix? https://www.raspberrypi.org/forums/viewtopic.php?f=78&t=63264 However, when it comes to this pipeline: antiprism generating program -> OFF file -> off2pov -> POV -> povray things are working great: https://flic.kr/p/LoXhEG Kirby

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another Raspbian Recipe
by kirby urner 26 Aug '16

26 Aug '16

I did get povray 3.7 to compile on the Jessie distro that came with my Pi2. I'll link to another location for the details as this is not 100% about Python. Note however my link to the POV-Ray + Python stuff at my Oregon Curriculum Network website. https://www.raspberrypi.org/forums/viewtopic.php?p=1029037#p1029037 Adrian has written back to say the Github repo for Antiprism (linked from antiprism.com) no longer requires that special CPPFLAGS switch. Just ./configure should do the job (see previously posted Raspbian Recipe). These resources complement the Pi3D library, which is more like VPython (which might compile also?, now that I have boost?). Kirby

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a Raspbian recipe for geometry teachers
by kirby urner 25 Aug '16

25 Aug '16

You might wonder what this has to do with Python, see notes at the end for a pure Python code stash. We also tend to think of the Raspberry Pi as a "Python computer" so anything Raspbian is of potential interest. Antiprism will convert OFF (geometry) files to POV (ray tracing) files. The Python + POV-ray synergy is still viable, though I've not attempted that. Looks like my next project, following the recipe here: https://www.raspberrypi.org/forums/viewtopic.php?f=63&t=100529 In the meantime, lets do a workout using basic development tools: Unzip Adrian's tar.gz file from antiprism.com or clone his Github repository, and then install a GLUT clone if you don't already have one (the configure step will say it can't build antiview if you don't). sudo apt-get install freeglut3-dev g++ Then configure / compile / install: CPPFLAGS="-fsigned-char" ./configure make sudo make install-strip sudo ldconfig Read the docs and look at the many screen shots on his website for what you'll be able to do after that. In my case the Pi may simply generate OFF files, transform them into POV files, then offload to another machine for actual rendering. Screen shots: https://flic.kr/p/Ln3zeL https://flic.kr/p/Lom9uH Notes: I started with a plain vanilla Jessie distro of Raspbian. The steps above, including the need to maybe run ldconfig are spelled out in Adrian's README, which I suggest you go to first thing, if undertaking this cooking exercise. For math teachers new to "gnu math": some of the steps in the above recipe take quite awhile, starting with that very first process: getting a free OpenGL implementation. I went out and did yard and gardening work during the make step. Partake of some school-approved beverage and kick back. During ./configure, the script may appear to hang at some point at: fi (the end of a bash script if block i.e. if .... fi marks a block) and you'll maybe wonder if it's up to you to perform an intervention. Have faith, the script will say done when it's finished. The CPPFLAGS="-fsigned-char" relates to this issue: http://blog.cdleary.com/2012/11/arm-chars-are-unsigned-by-default/ Adrian diagnosed the issue only hours ago. Without that switch, it'll compile, and all the --help switches will work, but the many programs will report a command line error and not actually do the work. Adrian was able to grok the problem even without owning a Pi. He used this emulator instead: https://wiki.debian.org/RaspberryPi/qemu-user-static Many thanks to Adrian Rossiter for this brilliant and well-maintained spatial geometry library. He also has a large stash of free Python programs that cover some of this same territory: https://github.com/antiprism/antiprism_python/blob/master/README.md Kirby Urner @4DsolutionsPDX Portland Knowledge Lab VLM (a type of PWS) in Portland, Oregon

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Fwd: Doing Math with Python at PyCon Education Seminar
by kirby urner 19 Aug '16

19 Aug '16

On Thu, Aug 18, 2016 at 11:09 PM, Amit Saha <amitsaha.in(a)gmail.com> wrote: > > Thank you! I think i have to start using Jupyter more so that I know > how to make the best use of it or troubleshoot it when it hangs and > even a kernel restart won;t help! But really love how it allows me to > show the code and output together. I started using a custom.css file > to increase the font size, so definitely improvement for me. > > Yes, Jupyter is a part of the puzzle, when it comes to workflow, among students and teachers. I imagine students each booting the same Notebook on localhost while a teacher walks them through it on a big screen, demonstrating how it might be used and underlining what it teaches. However this model presumes each student has some localhost to boot jupyter-notebooks on. Is that a given. Will Chromebooks work? Can I run Anaconda on a Pi? This model could all be in lieu of, and/or in addition to, turning to page such and such in a non-interactive textbook, where no coding language is communicated, other than in non-executing typography. My attitude is not "here's how you must organize the workflow" so much as "lets innovate and experiment and learn all we can from each other, compare notes". However, creating a climate wherein innovation and experimentation are encouraged is no simple matter. We start with a stereotypical classroom wherein a single teacher is running in place on a treadmill (figuratively), with a set curriculum. There's plenty to do, a full plate, and "learning to code" is neither expected nor rewarded. The curriculum is the one thing a busy math teacher maybe doesn't need to spend extra time on, as the curriculum is handed down from above. That's the rock. The school district picks the textbook, not the teacher. I'm thinking we need keep a lot of "the rock" in terms of topics and their interconnections (what passes for highs school mathematics in our day) but then slide in this new tool layer based on Jupyter Notebooks in place of a scientific calculator, per your talk. That's a challenge however, and I think we need to broaden the consensus that "learning to code" and "learning math" are indeed consistent goals, synergetic in fact (whole > parts). The New Math cohort in 1960s US, was too "top down" in retrospect. I benefited from that curriculum (briefly, before transferring to Junior English School of Rome), a complete overhaul of the curriculum in reaction to Sputnik. The US had panic attack, ala War of the Worlds with Orson Welles.[1] But today, with China having just launched a first satellite aimed at testing quantum encryption technology, we're not just in some "history repeats itself" cycle. History spirals more than circles. For a shift in the math curriculum to happen (yet again), we need to stop "waiting for superman" in the guise of some army of computer scientists that will suddenly show up to develop an entirely new high school track called "computer science". Yes, we have AP CS, but it's nothing mainstream, doesn't come with math credit in most states, and is really more just Java-based computer science, not really high school mathematics with Jupyter Notebooks and Python. By expanding the mathematics offerings to include these "math through coding" experiments, we have the ability to leverage existing resources, meaning teachers already in the math teaching profession. That's close enough to work with. This was never a static field. Ultimately the goal is to rescue mathematics from its current status as "mandatory yet off-putting". I'm wanting math teachers themselves to drive the process, so grass-roots, not top-down. They'll be better positioned having made this investment. Learning to code is a positive career move for them as well. A somewhat different approach is to start with a different STEM subject, such as chemistry or physics, and using Jupyter Notebooks to teach that. I'm on a listserv for Physics teachers and have posted links to my Notebooks, for those maybe unfamiliar with this option. The scipy stack will then follow them on into college. Kirby I tweet this out every so often, including @MAAnow and @Teacher2Teacher etc. https://medium.com/@kirbyurner/the-plight-of-high-school-math-teachers- c0faf0a6efe6#.nfc8qv4hg

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Doing Math with Python at PyCon Education Seminar
by Amit Saha 19 Aug '16

19 Aug '16

Hey all, I spoke at the PyCon Australia Education Seminar. I really loved the energy of all the speakers. All the talks are here at: https://www.youtube.com/playlist?list=PLs4CJRBY5F1Jh6fFqT1p5TZRx5q06CcaR My talk is here: https://www.youtube.com/watch?v=XJOt4QQgx0A with the slides and demos here at https://github.com/doingmathwithpython/pycon-au-2016 Best Wishes, Amit. -- http://echorand.me

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rounding out a Python course...
by kirby urner 17 Aug '16

17 Aug '16

Having explored Jupyter Notebooks, our next task was to dissect a simple Flask application, with an API published here: http://thekirbster.pythonanywhere.com The goal with my campers is to get them used to self-hosting, serving solo, with a server process on localhost, then deploy, most straightforwardly from Anaconda Spyder to Pythonanywhere in my experience, though I also enjoy Eclipse, Pycharm and other IDEs. https://flic.kr/p/EebhmS When working with Python beginners, I don't insist on bringing in Github or any version control right away. Unittesting with Pyunit, yes, we got to that (in a Jupyter Notebook): http://nbviewer.jupyter.org/github/4dsolutions/Python5/blob/master/Atoms%20… Shortened: http://goo.gl/nek3Uf But actively using Github, in a 40 hour course on Python, is not required. Pythonanywhere lets us copy files from localhost to the server with a capable GUI all its own. My Flask application carries on with the Periodic Table of Elements, fleshed out as lists, tuples, namedTuples, then as a class (with __getitem__ to mirror namedTuple behavior). We study I/O in terms of reading/writing JSON files, with a quick look at pickle (just for contrast, of what it's like to archive full Python objects). I emphasize the security aspects of JSON: in being so low level, it's not about sneaking in runnable code. The advantage of stretching to Flask, is that whereas all the running code the students look at is pure Python, I show them where the JavaScript would go, in /static/js, to be imported by the html5 / jinja2 templates (as well as the css). PythonAnywhere is already set up to host Flask applications. They only take minutes to set up. One of my students had an application going within the course of the 3-lab session. I told the students it was OK to mess up the periodic table with bogus data and indeed one of the elements has 1009 protons I think it is. We were able to POST to the SQLite database with code this simple (you're welcome to try, just for fun (the data may go away when I swap in a new copy, or I may change the "secret security word" -- there's no login). It won't accept elements already posted. Simple client (programmaticly POST, no actual browser form used). # -*- coding: utf-8 -*- """ Created on Fri Jul 29 17:35:58 2016 @author: Kirby Urner Post a chemical element to the Periodic Table. Goes into sqlite DB Periodic_table.Elements API: HTML views /elements /elements/H /elements/Si ... /elements/all JSON output /api/elements?elem=H /api/elements?elem=O ... /api/elements?elem=all Requires: flask_app.py <--- uses flask (conda install flask) connector.py Databases (SQLite) glossary.db <--- these may need to go in home dir periodic_table.db Jinja2 templates /templates/ home.html elements.html elem_page.html all_elems.html glossary.html """ import requests data = {} data["protons"]=81 data["symbol"]="Tl" data["long_name"]="Thallium" data["mass"]=204.3833 data["series"]="Post-transition metal" data["secret"]="DADA" # <--- primitive authentication # the_url = 'http://localhost:5000/api/elements' the_url = 'http://thekirbster.pythonanywhere.com/api/elements' r = requests.post(the_url, data=data) print(r.status_code) print(r.content) PS: here's from my review of decorators from last night, written live while I chatted: # -*- coding: utf-8 -*- """ Created on Tue Aug 2 20:58:29 2016 @author: kurner """ def UFO(arg): def eater(f): f.note = arg return f return eater @UFO("I've been abucted") def innocent_bystander(): print("Hello world") print(innocent_bystander()) print(innocent_bystander.note) ==== # -*- coding: utf-8 -*- """ Created on Tue Aug 2, 2016 Course: PYT-PR (Saisoft.net) Session 09 Kirby Urner Instructor: kirby.urner(a)gmail.com @thekirbster Audio Check (6:15 PM PDT) Introduction: Python in the Ecosystem (continued) PythonAnywhere + Github + Flask Jupyter Notebooks Batteries Included: SQLite (sqlite3) Web Dev: Dissecting a Flask application LAB 1: get a Flask application up & running on localhost Reviewing Decorators LAB 2: use Flask client to add to Periodic_table.db Another look at Pythons "scaffolding" (__rib__ cage): The Permutation class ("word scrambles") (more concepts through Cryptography & Group Theory) LAB 3: doodle period: encode and decode various phrases Play with web app more. Pythonanywhere anyone? Summary of Session 09 """

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PyCharm EDU
by Jurgis Pralgauskis 15 Aug '16

15 Aug '16

Hi, It proposes interesting approach with tasks/exercises course with automated checking. https://blog.jetbrains.com/pycharm/2016/08/welcome-pycharm-edu-3/ https://www.jetbrains.com/pycharm-edu/quickstart/ -- Jurgis Pralgauskis tel: 8-616 77613; Don't worry, be happy and make things better ;) http://galvosukykla.lt

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