Mailman 3 February 2002 - Edu-sig

Analyzing algorithms...
by Jeffrey Elkner 25 Mar '02

25 Mar '02

After attending Pai Chou's wonderful presentation, "Algorithm Education in Python" at Python10, I got permission from the instructor of an algorithms course I am currently taking to do our programming assignments in Python (after first assuring him that they would not be difficult to read ;-) Our first assignment is to implement merge and heap sort and then to compare them empirically as to the number of assignments and comparisons made by each. I've written the sorts. Does anyone have any suggestions as to the best way to do the empirical analysis? Is there a better way than just creating counters and then littering my code with increment statements? Please let me know if you have any ideas? Thanks! jeff elkner yorktown high school arlington, va

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OnLisp
by Dethe Elza 26 Feb '02

26 Feb '02

You can download Paul Graham's out-of-print book On Lisp. I found out about this from an interesting weblog called "Everything Burns" (http://jimfl.tensegrity.net/), which had this to say about it: <quote> I esteem OnLisp to be one of the most well-written, compelling books I have encountered on any topic in computing. This is no mean praise considering various works by one Stanford Professor name of Knuth. You don't really have to care much about Lisp or its variants to enjoy this book, though you should, at least, be able to tolerate topics which arise from the peculiarities in Lisp-shaped languages. Familiarity with Lisp will serve a programmer in any language anyway. Sadly, OnLisp is out of print, but you can download it free of charge. You will be missing only the weight of the dense paperback in your hands, the attractive cover, and the few figures sprinkled throughout. </quote> http://www.paulgraham.com/onlisptext.html --Dethe -- Dethe Elza (delza(a)burningtiger.com) Chief Mad Scientist Burning Tiger Technologies (http://www.burningtiger.com) Weblog: http://livingcode.manilasites.com/

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Music and Computers - an online text
by Jason Cunliffe 25 Feb '02

25 Feb '02

http://eamusic.dartmouth.edu/~book/ to be used with Jsyn http://www.softsynth.com/jsyn/plugins/ ./Jason ______________________________________________ Jason Cunliffe [NOMADICS: Director art+design] tel/fax: +1 718 422-1078 jasonic(a)nomadics.org N 43:00.000' W 074:31.875' ALT:1144 ft 84 Henry Street #3C Brooklyn NY 11201 USA

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Re: Tkinter and IDLE
by Lloyd Hugh Allen 25 Feb '02

25 Feb '02

I seem to recall someone on the tutor list suggesting way back that if you comment out the mainloop() of a Tkinter program, it will (usually) work fine under IDLE. The issue is that IDLE uses Tkinter itself, and python gets confused when two mainloop()s are running (rather, gets confused when you try to shut one of them down).

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IDLE problems with Tkinter
by Tim Wilson 22 Feb '02

22 Feb '02

Hi everyone, My students have used IDLE for all their editing to this point. Now we're getting to the point of playing with Tkinter a bit and I find that many, if not all, of the Tkinter apps I try don't exit cleaning and end up hanging IDLE. We're using Python 2.2 on Win95, but the same thing happend with Win98. Running the programs from the DOS shell seems to work fine. Is this a known problem with IDLE? I'm including a short script below that exemplifies the problem. The code is from Wesley Chun's Core Python book. from Tkinter import * def resize(ev=None): label.config(font='Helvetica -%d bold' % scale.get()) top = Tk() top.geometry('250x150') label= Label(top, text="Hello World!", font='Helvetica -12 bold') label.pack(fill=Y, expand=1) scale = Scale(top, from_=10, to=40, orient=HORIZONTAL, command=resize) scale.set(12) scale.pack(fill=X, expand=1) quit = Button(top, text="Quit", command=top.quit, activebackground='red', activeforeground='white') quit.pack() mainloop() Thanks for any input anyone can provide. -Tim -- Tim Wilson | Visit Sibley online: | Check out: Henry Sibley HS | http://www.isd197.org | http://www.zope.com W. St. Paul, MN | | http://slashdot.org wilson(a)visi.com | <dtml-var pithy_quote> | http://linux.com

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RE: [Tutor] style question
by alan.gauld＠bt.com 22 Feb '02

22 Feb '02

> some feedbakc. Let's say you have a task of finding out how many of 5 > positive integer numbers (a-e) are even. Which (if either) of the two > codes would be preferred: > > # {option A} > odd=a%2+b%2+c%2+d%2+e%2 > even=5-odd Yech! I don't like this under any circumstance. If I really wanted to do it in two lines I'd try something like: >>> count = 0 >>> L = [a,b,c,d,e] >>> for n in L: if n%2: count += 1 > # {option B} > if a%2==0: > even = even + 1 > if b%2==0: > even = even + 1 > if c%2==0: > even = even + 1 > if d%2==0: > even = even + 1 > if e%2==0: > even = even + 1 This is the same as above but writing the loop longhand... > Is option A guilty of relying on the "side effect" of mod 2 > being a 1 or zero or is this a desireable/understandable > use of this function's return It's an acceptable use but just plain obtuse. The minor gain in performance over the loop doesn't justify the loss of readability IMHO. Alan g

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Re: Executable pseudocode / executable flowcharts
by Daniel Ajoy 21 Feb '02

21 Feb '02

Executable pseudocode / executable flowcharts (Kirby Urner) > Agilent has a product (looks like a reincarnation of what > was formerly HP VEE) that allows graphical programming by > hooking boxes together, using conditional branching. The > same idea of user-definable parameters per box is implemented. > Here the boxes may contain signal processing algorithms, > such as a Fourier Transform or something. This is also about boxes to represent programs: http://www.soe.berkeley.edu/~boxer/ "20 Reasons to use Boxer (Instead of Logo)" ftp://soe.berkeley.edu/pub/boxer/Distribution/20reasons.pdf Daniel

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Re: [Edu-sig] style question
by Kirby Urner 20 Feb '02

20 Feb '02

> Which (if either) of the two >codes would be preferred: I agree with Danny that a list-based approach would be better: from operator import add def check(testlist): return reduce(add,[i%2==0 for i in testlist]) >>> check([1,4,5,9,3,8,7]) 2 Kirby

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style question
by Christopher Smith 20 Feb '02

20 Feb '02

I have a question of style and am wondering if you would consider giving some feedbakc. Let's say you have a task of finding out how many of 5 positive integer numbers (a-e) are even. Which (if either) of the two codes would be preferred: # {option A} odd=a%2+b%2+c%2+d%2+e%2 even=5-odd # {option B} if a%2==0: even = even + 1 if b%2==0: even = even + 1 if c%2==0: even = even + 1 if d%2==0: even = even + 1 if e%2==0: even = even + 1 odd = 5 - even Is option A guilty of relying on the "side effect" of mod 2 being a 1 or zero or is this a desireable/understandable use of this function's return value? /c

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Another example of Python at work
by Kirby Urner 19 Feb '02

19 Feb '02

Just to toss out another example of a project wherein Python is proving very useful as a "glue language", I offer my: http://www.inetarena.com/~pdx4d/ocn/sphpacking.html What's going on here is we have this Java applet that packs spheres in a particular way. We want to use its data to feed another free software package called Qhull, and we want to view the results using free rendering software (Povray) and VRML. So Python comes in and does all the mediation between the apps, reading sphere data, doing computations, passing data out to Qhull, reading it back in, and so on. It's the kind of thing that you want to do fairly quickly, and without trying to memorialize the whole process in some perfect code. A little worse (than perfect) is better in this case. Also, thanks to object-orientation, it's natural to define "Ball" objects which correspond to the balls in the packing. These get properties and methods related to finding all nearby neighbors, and for rendering the results. Python fits the problem, because it fits your brain (or mine at least). Kirby

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