Mailman 3 July 2004 - Edu-sig

Re: [Tutor] what? (late nite entertainment) (*)
by Gregor Lingl 25 Mar '05

25 Mar '05

Now: early morning corrections ... Alfred Milgrom wrote: > Hi Gregor: > > Hard to work out what is what :) as there seems to be a typo in one > line of your code: > > if x[z]: x[z*z:n:z]=y[z*z:n:z] > > (At least it doesn't work on my machine with Python 2.2) > Yeah, I had the idea when playing around with some new features of Python 2.3, as I do sometimes late at night - before shutting down my computer. This one I found at: http://www.python.org/doc/2.3.3/whatsnew/section-slices.html and I looked for an example for use of "assignment with extended slices" ... > Also the subroutine breaks for n = 1 or less. > Maybe you need a line at the start to say > if n <2 : return [0] > what() was intended to generate all primes less than n. (In fact it's an implementation of the sieve of Eratosthenes). The bugs came not only from not beeing interested in primes less than 2 ;-) but also from beeing a little tired already. Sorry. I think the following version repairs that - and hopefully uses less obfuscating variable names (which in fact originally was part of the "riddle"): def primes(n): sieve, zeros = range(n), [0]*n sieve[:2]= 0,0 i = 1 while i*i < n: if sieve[i]: sieve[i*i:n:i]=zeros[i*i:n:i] i += 1 return [p for p in sieve if p] Regards, Gregor >

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Re: Introductory high school programming
by Darren Payne 01 Aug '04

01 Aug '04

See topics & msgs below to put my comments in context. I have been a member of this group for quite a while and content myself with reading the interesting things people have to say. Now I would like to add some of my experiences for others to consider. I teach computing to high school students in Australia (Sydney, NSW actually). I currently work in a "selective" school - US readers would understand this better as magnet school. Entry is gained via a battery of tests & positions offered. A few years ago I completed post grad study in gifted ed - at the end was invited to write a 2 day unit to be used in the university's gifted program. I have taken up this offer and based it on work by Jeff Spence (Canadian guy on exchange in my hometown a few years back) Anyway - I have been using Java and have reasonably successfully taught an introduction to Java - as a first language - to 10 and 11 year old children. This year I decided I would introduce my year 7 classes to Java. Now, after one term (10 weeks), I fear it is just too difficult. In essence, the more Java I learn the less I like Java. The decision to go with Java was encouraged by my current yr12 class whom last year were determined to learn a "real" language AKA C++. I compromised and "taught" them Java. Only one of these students has put in enough effort to establish any level of skill with the language. I really wanted to show them Python. Last year (as well - in parallel to yr12) I started teaching Python as a first language to my yr9 (now yr10) class - they loved it and I enjoyed teaching it. Re Scheme; my yr12 class also do an option involving different paradigms - one of these is the functional paradigm. So I teach Haskell. I really like it, I like the way it makes me think. Because the students can be examined on either Hskell or Scheme (Lisp) I also show them some Scheme - but prefer Haskell becasue no reverse Polish notation and no brackets! In summary, I have found Python far and away to be the best language for high school students. It is powerful, easy to use, has clear simple syntax that doesn't "get in the way", is extendable with loads of other modules, has an active developer community, is open source so I can burn it CD and legally give it to kids to take home and so much more. Perhaps best of all it teaches the major, MODERN CONCEPTS in programming and these are easily transferred to other languages. I don't like Java (read this like "tiggers don't like Java" - I have a 3 yr old and 4 old!)- it is all just hype and we have all been suckered in. Compiler errors are a hassle for students - interpreted is much better during learning & development of programs. Being forced to use OO for even trivial programs puts too much overhead in the way of learning to program. Python overcomes this because OO is optional - you don't have to use it with trivial programs. Anyway - enough from me at this point. Hope this offers a semi empirical flavour to the discussion. regards P.S. - consider Python Programming for absolute beginner by Michael Dawson as a text. Darren Payne Hurlstone Agricultural High School > > > Today's Topics: > > 1. Introductory high school programming class - > Python or > TeachScheme (Joseph Ehlers) > 2. Python for High School Students (Garret > McGraw) > 3. RE: Introductory high school programming class > - Python > orTeachScheme (Kirby Urner) > 4. RE: Introductory high school programming class > - Python > orTeachScheme (Liow, Dr. Yihsiang) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Wed, 5 May 2004 20:48:25 -0500 > From: "Joseph Ehlers" <ehlersjp(a)msn.com> > Subject: [Edu-sig] Introductory high school > programming class - Python > or TeachScheme > To: <edu-sig(a)python.org> > Message-ID: > <BAY4-DAV64OgRGkQ6mB00001262(a)hotmail.com> > Content-Type: text/plain; charset="iso-8859-1" > > I'm trying to propose an introductory computer > programming class for high school students. I do > not have a programming background so I will be > learning the language just like the students. > Through my research I came across Python. It sounds > great - easy to learn, teaches thinking skills, and > is fun. I was set to go with Python then I came > across the TeachScheme project which also sounds > great - it too is easy to learn, teaches thinking > skills and comes with lots of curriculum. I have a > few questions and I'm hoping this group can shed > some light on this issue. > > 1. Is one better than the other (Python vs. > TeachScheme) to teach high school novices > programming skills, thinking skills, language, and > keeping their attention so I can then have an > audience for a second, more advanced programming > class? > > 2. I've looked at "How to Think Like a Computer > Scientist", it looks very doable for a novice and > "Python Programming for the Absolute Beginner" > (Premier Press) looks like a lot of fun. Is there > any other curriculum for high school students out > there? > > 3. Is it possible to teach a semester of > TeachScheme and a semester of Python or is that > overkill on the basics and not doing justice to > either program? > > I appreciate your assistance. >

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Re: Teaching graphics with Python (was Introductoryhighschool programming)
by Arthur 01 Aug '04

01 Aug '04

> I wanted to thank you for this stereoscopic feature in VPython, and > suggestion that I use it. Just thought I'd mention that VPython 3.0 has been released last week. This version is mostly a behind the scenes revamp of the code. VPython now uses the Boost Python library to expose Vpython's cvisual C++ code to Python. Among other things this allows one to directly subclass cvisual primitives in pure Python. Currently this is an undocumented facility as to VPython. But getting it down to its essentials, the following runs, and provides a sphere primitive that insists on being blue. import cvisual import time import atexit def __waitclose(): while not cvisual.allclosed(): time.sleep(0.05) atexit.register(__waitclose) scene = cvisual.display() class sphere (cvisual.sphere): def __init__( self,*args,**keywords): cvisual.sphere.__init__(self) self.color=(0,0,1) self.complete_init( self, self, 1, scene, None) s=sphere() Seems to me this facility will open up interesting new possibilities in having fun with VPython/cvisual. PyGeo for example could now decide to more truly wrap the cvisual library, as opposed to using it - through Vpython - as a rendering back-end. > > My slides are here: > http://www.4dsolutions.net/oscon2004/ (might be some minor problems if > viewed in Windows, not sure (tried to make it work well in both, but > kept finding little discrepancies going back and forth, and did all > last minute editing on the Linux side)). Looks super. Art

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How to evaluate programming skills, are there any international benchmarks?
by Linda Grandell 27 Jul '04

27 Jul '04

Hello everybody, I have been going through the edu-sig archive for a couple of months now; there is really a lot to read and learn in there. I work at the Department of Computer Science at Åbo Akademi University in Turku, Finland. For the last two years I have been active in a project, whose aim is to acquaint high school students with computer science, since no true computer science education is available to them otherwise. While working with these high school students I have realized how important it would be for them to get a true and correct conception of what computer science is all about. I think the idea of CP4E, proposed by Guido van Rossum, is very good. I believe that everybody (not only future computer scientist) would gain from knowing how to program, due to the meta skills learned in the process. When one learns to program one also acquires knowledge in how to solve problems, think logically, methodically and algorithmically. I think the basic education in computer science has not been given enough attention; in my opinion the basic computer science courses should have high priority, since they act as starting points into the field. I feel that programming should be taught in high schools, since these should provide all-round learning and ensure that the students receive the skills and knowledge needed for further study and in life in general. The reason I am telling you all this is to set some kind of background to what I want to ask you about. I am about to engage myself in research as a PhD-student, focusing on how programming and algorithmic thinking can be taught to high school students. I have been very fascinated by Python, and have decided to use that as the first thing to try out in order to get some results on how high school students should (or shouldn't :) be taught. I will start by developing a course in Python that I will give to newbies in high schools. I have not had any problem in finding material for the course, but what I do see as a problem is how I should go about evaluating the course. Since I am aiming at a PhD, I would, naturally, like to be able to extract some information about whether the course promoted the problem solving, programming and algorithmic thinking skills of the students. Since there are a lot of different persons on this mailing list, I thought it would be a good idea to write down my ponderings here. * Have anybody else done anything like what I am about to do? I would really like to hear about your experiences. * Are there any international benchmarks one can use to measure the results of this kind of an "experiment"? What should be measured and how? * What kind of research methods can and should be used? * The course will contain about 28-30 hours; I have a feeling that we will be able to cover much more programming theory using Python than, for instance, Java, but does anybody have an idea about how far we could get in that time? I am very enthusiastic about this project and I am really looking forward to giving the course. I am grateful for any answers, thoughts and advice you can give me. Best regards, Linda Grandell Åbo Akademi University Turku, Finland

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Re: Edu-sig Digest, Vol 12, Issue 5
by Darren Payne 25 Jul '04

25 Jul '04

Ken, I feel you may obtain the desired / expected result if you use elif instead of if ... other than the first if statement of course. e.g. if dirnpoint > xx: do this elif dirnpoint > xx: do that elif ......: do this instead give it a go and see what happens. regards Darren Payne Hurlstone Ag. ===== ----------------------------------------------------------------------------------- regards Darren Payne Hurlstone Agricultural High School Ph: 9829 9222 Fax: 98292026 __________________________________ Do you Yahoo!? New and Improved Yahoo! Mail - 100MB free storage! http://promotions.yahoo.com/new_mail

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Re: Re: [Edu-sig] problem with IF
by Kent Johnson 24 Jul '04

24 Jul '04

I cant' resist either. Here is the way I would do it. def degreesToDirection(deg): dirs = ['N', 'NE', 'E', 'SE', 'S', 'SW', 'W', 'NW', 'N'] ix = (int(deg) + 23) / 45 return dirs[ix] To test: for deg in [0, 21, 22, 45, 66, 67, 90, 135, 180, 225, 270, 315, 360]: print deg, degreesToDirection(deg) 0 N 21 N 22 NE 45 NE 66 NE 67 E 90 E 135 SE 180 S 225 SW 270 W 315 NW 360 N By the way this points out that the cutoff points in the original post are not evenly spaced and probably not what is wanted. It's easy to have Python tell you the correct cutoffs: >>> [ (45*i)+22 for i in range(8) ] [22, 67, 112, 157, 202, 247, 292, 337] Kent > ps. I can't help thinking there may be a more elegant way of doing the > bearing conversion. >

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problem with IF
by ken 24 Jul '04

24 Jul '04

hello all, I have been trying to write a program to display the reading from a weather station. I was trying to change the direction of the wind from degrees to points of compass. Have tried various if.. elif.. but it seems to take the last option in the list regardless of the value of the degrees. # let's put in points of compass, instead of degrees dirnPoint = "N" print dirn if dirn >= 22: dirnPoint = "NE" print dirnPoint if dirn >77 : dirnPoint = "E" print dirnPoint if dirn >112 : dirnPoint = "SE" print dirnPoint if dirn > 157 : dirnPoint = "S" print dirnPoint if dirn > 202 : dirnPoint = "SW" print dirnPoint if dirn > 247: dirnPoint = "W" print dirnPoint if dirn > 292: dirnPoint = "NW" print dirnPoint if dirn > 345: dirnPoint = "N" print dirnPoint print dirn I added the prints to follow the progress through the chioces. Below is the printout from a sample direction;301 NE E SE S SW W NW N 301 To my way of thinking, it should have stopped at "W" but it seems to be getting TRUE for > 292 and > 345. Any ideas, please. Thanks.. ken Wallwork Computing Studies Co-ordinator St Joseph's College Hunters Hill NSW Australia ken(a)joeys.org ken(a)wyverntech.com

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Subject: Re: [Edu-sig] problem with IF
by Lloyd Hugh Allen 23 Jul '04

23 Jul '04

Two things. First, you want to use elif. Second, you want to go from most specific to least specific (or else to use a pair of bounds). I'm going to use a different example, because it would take too long to talk about eight cases. I think that you might have started with a nested if, but that will barely fit on your screen after eight indentations... Let's say that one is one, two is a couple, and three is many. I want to know how many widgets I have, and I'll start with what you have and see what happens. widget = 5 if widget >= 1: print "I have one widget" if widget >= 2: print "I have a couple of widgets" if widget >= 3: print "I have many widgets" and then the program dutifully prints I have one widget I have a couple of widgets I have many widgets This is a problem. We only want one case. To guarantee mutual exclusivity, we use elif, which is an abbreviation for else if. widget = 5 if widget >= 1: print "I have one widget" elif widget >=2: print "I have a couple of widgets" elif widget >=3: print "I have many widgets" except that now we get the unfortunate output I have one widget when we know in our heads that we have many widgets. This can be fixed by reversing the order of the cases--the condition widget >= 1 will be satisfied for every single value of widget that also >= 3, so we have to start with the widget >=3. widget = 5 if widget >= 3: print "I have many widgets" elif widget >=2: print "I have a couple of widgets" elif widget >=1: print "I have one widget" now the program hits the case that widget >= 3, sees that this is true, displays I have many widgets, and then STOPS. Which is good. It's also good to include an else at the end so that the program notifies you that an unexpected value (say, zero or a negative number) was encountered. widget = -5 if widget >= 3: print "I have many widgets" elif widget >= 2: print "I have a couple of widgets" elif widget >= 1: print "I have one widget" else: print "The value of widget is unexpected: " + `widget` the backquotes around the widget allow `widget` to act as a string; you can't otherwise concatenate a string with a numeric value, and I sense that I shouldn't talk about string formatting yet. And I'll ignore the possibility of a real-valued number of widgets--what would you do with 1.5 widgets anyway? Oh, and my email spell-checker went and turned all the "elif"s into "elf"s, so if I left an elf in there, please turn him back into an elif. Sorry. On an unrelated note: looking forward to Vancouver...looks like a good schedule. -Lloyd

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Snack question
by billwinn＠u.washington.edu 22 Jul '04

22 Jul '04

I'm a novice Python programmer who wants to use Snatch. I have everything installed correctly as far as I can tell. But when I try to play something I get an error that says I failed to set the number of channels. Here's what I get: >>> from Tkinter import * >>> root = Tk() >>> import tkSnack >>> tkSnack.initializeSnack(root) >>> snd=tkSnack.Sound() >>> snd.read('/usr/games/chromium/data/wav/music_game.wav') >>> snd.play() Traceback (most recent call last): File "<stdin>", line 1, in ? File "/usr/lib/python2.2/site-packages/tkSnack.py", line 277, in play self.tk.call((self.name, 'play') + self._options(kw)) TclError: Failed setting number of channels. Any help will be most welcome. Thanks, Bil *************************************************************** * William Winn, * * 412 Miller, College of Education, Box 353600, * * University of Washington, Seattle, WA, 98195, USA. * * 206 685-1185, FAX 206 543-8439, billwinn(a)u.washington.edu * ***************************************************************

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Re: VPython
by Scott David Daniels 16 Jul '04

16 Jul '04

Kirby Urner wrote: >> Do you know who I should contact <about permission to run povray> >> (I expect the answer is sure)? > > Not sure whom to contact, but I bet povray.org gives some ideas. > ... > My goal is to have the same process work on either platform. But in > distributing this code, I wouldn't try to distribute povray as something > hidden or behind the scenes. I'd just say "get POV-Ray and install it -- > you can use it for *lot's* of other things, then enter a path to it here: [ > ]." Well, after a huge delay due to their strangely reimplementing the contact method, I finally have our answer: > It sounds fine to me, this is the sort of thing we like to see POV-Ray > doing. Feel free. > > regards, > -- Chris I'll try and push my changes back to VPython's website, anything more to include? -Scott David Daniels Scott.Daniels(a)Acm.Org

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