Mailman 3 July 2005 - Edu-sig

More Pythonic Mathematics
by Kirby Urner July 28, 2005

July 28, 2005

This morning I posted to the Math Forum about how an algebra student, armed with Python, might explore 'composition of functions' using operator overloading. Wrap ordinary function definitions in the Function class below, and you still have __call__ (to get range outputs from domain inputs), plus you have the ability to write h = f * g where f and g and Function objects, and h is a new function object such that h(x) == f(g(x)) for all x. An important aspect of algebra is polymorphism around * and + (multiplication and addition). These become known in terms of their field, ring and group properties, somewhat obscuring their origins in basic arithmetic. We multiply matrices and polynomials, quaternions and permutations. Python's operator overloading makes it easier to see what's going on: we're putting the definition of __mul__ under the programmer-mathematician's control One of the most primitive of all functions is the mapping of letters to letters, e.g. A->R, B->Q, C->C, D->Z... according to whatever random shuffle. The composition of P1 and P2 then becomes the result of mapping A to R per P2, then R to whatever per P1 (say Z), such that A->Z is the result of P1 * P2. The notions of inverse and identity mapping are well defined. Group properties may be explored (the beginning of abstract algebra). Notice that my algebraic functions below (a quadratic and a linear) need to have their inverses specified by the programmer, should it be that negative powering is likely to happen (for example). Some languages attempt to provide this automatically in simple cases, leaving it to the user to supply it otherwise (I'm thinking of J in particular). I'm not trying to be that fancy. Kirby Relevant post to math-teach: http://mathforum.org/kb/plaintext.jspa?messageID=3863728 #===================================== >>> def f(x): return x*x >>> def g(x): return 2*x + 3 >>> class Function(object): def __init__(self, f, invf = None): self.f = f self.invf = invf def __call__(self,x): return self.f(x) def __mul__(self, other): def newf(x): return self.f( other.f(x)) return Function( newf ) def __pow__(self, exp): if exp==1: return self newself = Function(self.f) if exp < 1: newself = Function(self.invf) for i in range(exp-1): newself *= self return newself #--- composition of function objects using __mul__ >>> of = Function(f) >>> og = Function(g) >>> oh = of * og >>> oh(10) 529 >>> oj = og * of >>> oj(10) 203 >>> import math >>> def invf(x): return math.sqrt(x) #--- expanding to integer powers (including negative powers). >>> of = Function(f, invf) >>> newf = of**(-1) >>> h = newf * of >>> h(10) 10.0 >>> h(20) 20.0

1 1

Thinking about Open Source
by Kirby Urner July 28, 2005

July 28, 2005

I just read Andy Oram's article about an audience outburst after some guy at a Linux conference used Windows + PowerPoint to do a presentation: http://www.onlamp.com/pub/wlg/7438 I'll be interested what reactions I get to using a WinXP laptop to present at OSCON (I used a Linux box last year). My Toshiba Satellite is my best laptop by far, and though I *could* run my Python + Pygame presentation on my daughter's Compaq under Mandrake 9.2, that'd be less satisfying. Open Source is a layered affair, as Tim O'Reilly likes to point out. You've got this LAMP layer that's open, but then groups like Amazon and Google build these web applications that are not really open, even if they sit atop LAMP in a big way. Plus the chips are proprietary. And even when a layer is open, you *still* need years of training to dive in, in many cases. The idea that the OS kernel is free is a good one, but let's not forget that free means extrinsic barriers of secrecy and property rights have been addressed -- but there's *still* the intrinsic barrier of needing to learn how the kernel works, before you mess with it. The tension is between "information" and "knowledge." Source code on a hard drive is information that may turn into knowledge in the mind of someone who can read and understand it. FOSS is about making information freely available. But that doesn't remove the need for training and expertise. If you don't know how to read, Project Gutenberg won't be of such direct help or relevance. So Python source code provides this layer in the stack. I've got this presentation manager that runs on Linux or Windows or Mac. The content of the presentation may be closed, secret or otherwise restricted. The platform on which the Python runs may be more or less open (in the case of WinXP, it's closed). But in the middle, you've got code that a Python programmer might read and improve upon -- open source, released under the GPL. I think when humans encounter one another, this is a lot how it is: we'll be perfectly open about some things, closed about others. But the stuff we're open about may not register with others, as they're not prepared to deal with the information we're sharing. I talk about some area of math (open source) and they glaze over. Or they do, and I do. Only sometimes, do I freely communicate on a wavelength that another is equally able to interpret. In those times, a meeting of the minds occurs -- a rare enough event, especially among specialists with a lot of deep knowledge and divergent interests. Kirby

1 0

Re: Networking in DOSEMU
by Lee Harr July 24, 2005

July 24, 2005

>I want to ask something not concerning python. Here, you give yourself an excellent hint that this is the wrong place to ask this question. >actualy i want to know how can i connect to my novel server thru dosemu. Here, I am wondering if you mean Novell. Searching is facilitated by correct spelling of the thing you seek. Let's take a look... http://www.google.com/search?q=dosemu+mailing+list Strangely, not the first hit on google, but the 3rd hit looks pretty good: http://dosemu.sourceforge.net/mailinglist.html good luck! _________________________________________________________________ Don't just search. Find. Check out the new MSN Search! http://search.msn.com/

4 10

Re: [Edu-sig] Writing presentation manager for OSCON, in Pygame
by Rodrigo Dias Arruda Senra July 19, 2005

July 19, 2005

[ Kirby Urner ] ------------------------------------------------------------ | Interesting work Rodrigo. Thank you. By the way, I hope you have found your missing coat. (I was the one giving speech right after yours at Goteborg ;o) | My setup code is not so friendly. It is friendly enough to be weaved (someday) into my py2slide tool as something like: | def setscene14(s): | graphics = [] | for i in range(1,12): | filename = "cubanim"+str(i).zfill(2) | graphics.append(fpath + filename + ".png" ) | mobj0 = Content() | mobj0.content_type = 'autoflip' | mobj0.topleft = (400,100) | mobj0.imagelist = graphics | mobj0.milliseconds = 100 | .... | #cut anim1 = _(""" Closest Packing of Spheres ========================== .. scene:: setscene14 """) Therefore, I could mix classic static slides with *cool* live-action slides as long as the target format (in this case: pygame) supports it. ** off-topic, but education related --> from this point on ** By the way, I did not have the opportunity during Europython to tell you (Kirby) about an experiment I did here in Brazil while teaching introductory courses. So I'll dare telling it now to you and edu-sig as well. The motivation was the huge heterogeneity of students backgrounds in introductory courses. Some students knew how to program in C++, VB, PHP, etc while others barely had experience with computers (although that was an outlier). The idea is called: The Big Brother. It's goal is to foster experienced students to "adopt, tutor, and monitor" the development of less experienced students during the course. In the beginning of the course everybody took a clustering exam, to classify students into: experienced (big brothers), grey, newbie. Students in grey zone can choose not to participate, or to migrate for any of the other two clusters. The catch is the following: A fraction of the measured progress in the newbie's grades goes to its respective big brother's grades. There was a fierce battle to adopt the student that failed badly during the clustering exam. I beleive this is a win-win-win situation: - the teacher gets many free-of-charge assistants - newbies get the close attention they usually need - experienced students have a chance to earn extra credit I only had few opportunities to put that in practice. # One of them teaching Python to Comp.Science undergraduates. So if you like the idea, and do it, I'm interested in feedback. best regards, Rod Senra -- Rodrigo Senra <rsenra |at| acm.org> ------------------------------------------------ GPr Sistemas http://www.gpr.com.br Blog http://rodsenra.blogspot.com IC - Unicamp http://www.ic.unicamp.br/~921234 ------------------------------------------------

2 2

SOT: authoring course material
by Peter Bowyer July 18, 2005

July 18, 2005

Hi, As I sit down to write my course material I was wondering - what software do you use? Traditionally material in the physics department has always been written in LaTeX (uugh), with a printed copy given to the student, and a PDF of the printed copy available online. I need to produce a printable set of notes, but would also like to do a true web-based version. We've talked about testing the students with online multiple-choice quizzes and I'm keen to have expandable sections of the notes online (so the more advanced students don't have to read the basics, but can see advanced questions the others cannot). However, from past experience if there are not full printed notes there will be complaints, and as the computers aren't dual-monitor it would be hard to read online notes while working. What have you found works when teaching introductory programming? Also, have you found tools such as wikis useful when either developing the teaching material or writing the following report? Thanks, Peter

6 7

More news from Europython
by Kirby Urner July 6, 2005

July 6, 2005

So one of the biggest developments was Guido's approval to enhancements around 'yield', making a new gen.send(arg) method to supplement the already-defined gen.next(). gen.send(arg) will feed arguments to a yield *expression* i.e. a yield on the right side of an assignment operator, e.g. x = yield. gen.send(None) is equivalent to gen.next(). http://www.opensubscriber.com/message/patches@python.org/1624403.html http://www.python.org/peps/pep-0342.html I'm hoping we'll build some simpler examples than those provided in the PEP, using simple math concepts or just skeletal "means nothing" code. Kirby

1 0