Mailman 3 April 2010 - Edu-sig

calculus and not-calculus using Python
by kirby urner 20 Apr '10

20 Apr '10

I've mostly been writing about a new kind of math class at the high school level that distinguishes itself from the precalculus - calculus track. This has partly to do with politics, as I think it's easier to develop something new and set that alongside already existing options (traditional courses) than it is to introduce reforms in already "programmed" offerings. However, Python has some capabilities when it comes to calculus, in scipy and Sage for example. Plus it's of course easy to take anything one might do with a calculator in support of learning calculus concepts, and do that same thing in Python instead. This was somewhat my approach in writings I did on the catenary some years ago (the catenary is a curve similar to a parabola but different). http://www.4dsolutions.net/ocn/catenary.html At this point though, it's maybe a moot point whether we try to embrace more calculus with Python or not. The premise was doing something more exciting with technology than scientific calculators, introducing a real programming language, and yet having this considered a math class as much as a computer class. This was against the backdrop of the "math pipeline" being broken according to many criteria, i.e. in need of some upgrades. Some progress has been made in small niches, but in many respects the current mood is to freeze features i.e. the response to rapid change is to codify and pickle that which once was. So I'm back to thinking only brand new courses will have a chance. They have to be seen as new, and the expectation must be that new material will be covered. Perhaps for this reason I find myself venturing into Wolfram territory as he's always talking about his "new kind of science". Those little cellular automata studies are actually pretty easy to implement in Python (we've done it here on edu-sig, with John Zelle's graphics.py, PIL and native Tkinter). http://www.4dsolutions.net/presentations/holdenweb/mini_nks.py I'm going to say more about these calculus exercises at some point, not sure how soon. This relates to the thread about generating tables. That was pretty fruitful thread, glad so many jumped in. We need to see that in some ways having computers put out to text files is a way to get back to the good old days, when we could explore reams of data. What's better nowadays is we don't really need all that paper (lets not waste it). We have hard drives and LCDs instead. Kirby PS: found this old exhange with Matthias of DrScheme fame. He just got some prestigious award, per an announcement on math-thinking-l. ============= from scipy.integrate import quad, dblquad, Inf from numpy import arange from math import exp, log, pi, sin, cos def test0(): """ Integration example http://www.scipy.org/doc/api_docs/SciPy.integrate.quadpack.html """ def thefunc(x): return cos(x) for a in arange(0, 2*pi, 0.1): output = quad(thefunc, 0, a)[0] fmtstring = "Integral of cos(x) from 1 to {0} = {1}: sin({0}) = {2}" print fmtstring.format(a, output, sin(a)) def test1(): """ Integration example http://www.scipy.org/doc/api_docs/SciPy.integrate.quadpack.html """ def thefunc(x): return 1./x for a in range(1,21,2): output = quad(thefunc, 1, a)[0] fmtstring = "Integral of 1/x from 1 to {0} = {1}: ln({0}) = {2}" print fmtstring.format(a, output, log(a)) def test2(): """ Double integration example http://www.scipy.org/doc/api_docs/SciPy.integrate.quadpack.html """ def I(n): return dblquad(lambda t, x: exp(-x*t)/t**n, 0, Inf, lambda x: 1, lambda x: Inf) print I(4) print I(3) print I(2) def test3(): """ Double integration example same as above but without using lambda http://www.scipy.org/doc/api_docs/SciPy.integrate.quadpack.html """ def mkfunc(n): def thefunc(t, x): return exp(-x*t)/t**n return thefunc def xfrom(x): return 1 def xto(x): return Inf def I(n): thefunc = mkfunc(n) return dblquad(thefunc, 0, Inf, xfrom, xto) print I(4) print I(3) print I(2) def doall(): test0() #test1() #test2() #test3() if __name__ == '__main__': doall()

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Python Spirograph
by Daniel Ajoy 19 Apr '10

19 Apr '10

> From: Phil Wagner <philhwagner(a)gmail.com> > > Wrote this code after I was inspired by this webpage > http://www.math.com/students/wonders/spirographs.html. Had some initial > difficulties with memory but I discovered Psyco while reading "Dreaming in > Code" (recommended by this community). It can speed up your code and really > helped out with the rapid calculations and drawing for this program. > http://www.voidspace.org.uk/python/modules.shtml#psyco. I thought you had seen this: http://www.samstoybox.com/toys/Spirograph.html Daniel

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Python Spirograph
by Phil Wagner 18 Apr '10

18 Apr '10

Wrote this code after I was inspired by this webpage http://www.math.com/students/wonders/spirographs.html. Had some initial difficulties with memory but I discovered Psyco while reading "Dreaming in Code" (recommended by this community). It can speed up your code and really helped out with the rapid calculations and drawing for this program. http://www.voidspace.org.uk/python/modules.shtml#psyco. If you are running this code on a desktop you may or may not need it. If the GUI runs slow or not at all then choose the command line. Also if anyone knows how to optimize this code please let me know because it has me scratching my head. Most of my research said to just chalk this up to the pros and cons of Python vs C. Thanks for all the inspiration this community gives me. You all challenge me to push myself everyday. Phil #Spirograph Maker inspired by http://www.math.com/students/wonders/spirographs.html from visual import * from visual.controls import * from string import * iterations = input('How many iterations?') class spiro(): def __init__(self,iterations): self.R = 65.0 #Radius of Fixed Circle self.r = 43.0 #Radius of Moving Circle self.o = 75.0 #offset of pen point in moving circle self.iterations = iterations self.t = arange(0,self.iterations,1) self.drawing = curve(x = ((self.R+self.r)*cos(self.t) - (self.r+self.o)*cos(((self.R+self.r)/self.r)*self.t)), y = ((self.R+self.r)*sin(self.t) - (self.r+self.o)*sin(((self.R+self.r)/self.r)*self.t)), color = color.green) def fixedRadius(self,fRadius): if GUIquestion == 1: self.R = fRadius.value else: self.R = fRadius self.redraw() def rollingRadius(self,rRadius): if GUIquestion == 1: self.r = rRadius.value else: self.r = rRadius self.redraw() def penOffset(self,pOffset): if GUIquestion == 1: self.o = pOffset.value else: self.o = pOffset self.redraw() def redraw(self): self.drawing.x = ((self.R+self.r)*cos(self.t) - (self.r+self.o)*cos(((self.R+self.r)/self.r)*self.t)) self.drawing.y = ((self.R+self.r)*sin(self.t) - (self.r+self.o)*sin(((self.R+self.r)/self.r)*self.t)) class GUI(): def __init__(self): self.c = controls(x=0,y=0,width=400, height = 400, range=100) self.s1 = slider(pos=(0,40),width=7, length=40, axis=(1,0,0),min=1,max=100,action=lambda: Spirograph.fixedRadius(self.s1)) self.s2 = slider(pos=(0,0),width=7, length=40, axis=(1,0,0),min=1,max=100,action=lambda: Spirograph.rollingRadius(self.s2)) self.s3 = slider(pos=(0,-40),width=7, length=40, axis=(1,0,0),min=1,max=100,action=lambda: Spirograph.penOffset(self.s3)) self.fixedRadiusLabel = label(pos=self.s1.pos, display = self.c.display, text='Fixed Radius', line = 0, xoffset=0, yoffset=20, height=10, border=0) self.rollingRadiusLabel = label(pos=self.s2.pos, display = self.c.display, text='Rolling Radius', line = 0, xoffset=0, yoffset=20, height=10, border=0) self.penOffsetLabel = label(pos=self.s3.pos, display = self.c.display, text='Pre-Offset', line = 0, xoffset=0, yoffset=20, height=10, border=0) self.scene1 = display(title = 'Spirograph!', x=410, y=0, width=400, height = 400) self.scene1.select() memload = 0 memquestion = 0 GUIquestion = 0 while(memquestion == 0): memload = upper(raw_input('(H)igh Memory GUI or (L)ow Memory Command Line:')) if memload == 'H': memquestion = 1 GUIquestion = 1 psycoquestion = upper(raw_input('Do you have Psyco (the memory accelerator installed)? Yes or No:')) if (psycoquestion == 'Y') or (psycoquestion == 'YES'): import psyco psyco.full() WYSIWYG = GUI() Spirograph = spiro(iterations) qbutton = 0 while(qbutton == 0): WYSIWYG.c.interact() if memload == 'L': Spirograph = spiro(iterations) command = '' while(command !='Q'): print('Adjust which factor of the spirograph?') print('Fixed Radius =',Spirograph.R, ' Moving Radius=',Spirograph.r, ' Offset of Pen=', Spirograph.o) command = upper(raw_input('(F)ixed Radius, (M)oving Radius, (O)ffset of the Pen, (Q)uit?')) if command == 'I': value = input('What is the new value?') Spirograph.numIterations(value) if command == 'F': value = input('What is the new value?') Spirograph.fixedRadius(value) if command == 'M': value = input('What is the new value?') Spirograph.rollingRadius(value) if command == 'O': value = input('What is the new value?') Spirograph.penOffset(value) -- http://www.google.com/profiles/philhwagner http://staff.hthcv.hightechhigh.org/~pwagner/ (My Digital Portfolio)

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using Python as a calculator
by kirby urner 18 Apr '10

18 Apr '10

I think Guido was wise to start his tutorial by showing how we might use Python as a calculator. We might assume many students in this day and age are quite familiar with this device, and even if they're not, the text might project one, show a picture on the screen, if what these things used to look like (still do). However, one thing calculators lack over the old wood pulp textbooks are trig tables with multiple rows showing a lot of data at the same time. Their small "chat window" does not permit much data to be seen at one time. Back in the day, a student could run her finger down the rows, as the number of angular degrees increase from 0 to 60 and onward to 90, perhaps all the way around to 360. Going across the row, one would have sine and cosine, perhaps tangent. Having all the data visible at once, or spread across a few pages, inspired some insights and understanding, as one could see the trends in the numbers, plus these "click stop" rows where the numbers would suddenly be super easy, like 1/2 and 1/2 for both sine and cosine. Calculators don't give us that kind of output, but earlier office computing machines did have paper i/o, called a tape, usually a scroll mounted on a spool and fed through a small printer. As one added numbers, one printed to tape, perhaps a running total. The tape itself was a valuable item (especially once it had the data on it). Large computers came with line printers that hit on continuous feed paper with holes along both sides, often with green and white stripes. I will not try to recapitulate the long history of printing devices, except to point out that computers inherited them while slide rules and calculators did not. The equivalent in Python is stdout and/or some file in storage, on the hard drive or memory stick. The program output shown below would be an example of this kind of i/o. Notice that unless a file name is given (optional), the data is to stdout. I'm going to do a full 90 degrees, just to remind myself of the patterns students got in the old days, before trig tables were replaced with calculators, much as dial watches were replaced with digital ones (not necessarily a smart move in all cases). >>> imp.reload(newprint) <module 'newprint' from 'C:\Python26\lib\site-packages\newprint.py'> >>> newprint.trigtable(range(91), "trigtable.txt") The contents of trigtable.txt: 0 1.000000000 0.000000000 0.000000e+00 1 0.999847695 0.017452406 1.745506e-02 2 0.999390827 0.034899497 3.492077e-02 3 0.998629535 0.052335956 5.240778e-02 4 0.997564050 0.069756474 6.992681e-02 5 0.996194698 0.087155743 8.748866e-02 6 0.994521895 0.104528463 1.051042e-01 7 0.992546152 0.121869343 1.227846e-01 8 0.990268069 0.139173101 1.405408e-01 9 0.987688341 0.156434465 1.583844e-01 10 0.984807753 0.173648178 1.763270e-01 11 0.981627183 0.190808995 1.943803e-01 12 0.978147601 0.207911691 2.125566e-01 13 0.974370065 0.224951054 2.308682e-01 14 0.970295726 0.241921896 2.493280e-01 15 0.965925826 0.258819045 2.679492e-01 16 0.961261696 0.275637356 2.867454e-01 17 0.956304756 0.292371705 3.057307e-01 18 0.951056516 0.309016994 3.249197e-01 19 0.945518576 0.325568154 3.443276e-01 20 0.939692621 0.342020143 3.639702e-01 21 0.933580426 0.358367950 3.838640e-01 22 0.927183855 0.374606593 4.040262e-01 23 0.920504853 0.390731128 4.244748e-01 24 0.913545458 0.406736643 4.452287e-01 25 0.906307787 0.422618262 4.663077e-01 26 0.898794046 0.438371147 4.877326e-01 27 0.891006524 0.453990500 5.095254e-01 28 0.882947593 0.469471563 5.317094e-01 29 0.874619707 0.484809620 5.543091e-01 30 0.866025404 0.500000000 5.773503e-01 31 0.857167301 0.515038075 6.008606e-01 32 0.848048096 0.529919264 6.248694e-01 33 0.838670568 0.544639035 6.494076e-01 34 0.829037573 0.559192903 6.745085e-01 35 0.819152044 0.573576436 7.002075e-01 36 0.809016994 0.587785252 7.265425e-01 37 0.798635510 0.601815023 7.535541e-01 38 0.788010754 0.615661475 7.812856e-01 39 0.777145961 0.629320391 8.097840e-01 40 0.766044443 0.642787610 8.390996e-01 41 0.754709580 0.656059029 8.692867e-01 42 0.743144825 0.669130606 9.004040e-01 43 0.731353702 0.681998360 9.325151e-01 44 0.719339800 0.694658370 9.656888e-01 45 0.707106781 0.707106781 1.000000e+00 46 0.694658370 0.719339800 1.035530e+00 47 0.681998360 0.731353702 1.072369e+00 48 0.669130606 0.743144825 1.110613e+00 49 0.656059029 0.754709580 1.150368e+00 50 0.642787610 0.766044443 1.191754e+00 51 0.629320391 0.777145961 1.234897e+00 52 0.615661475 0.788010754 1.279942e+00 53 0.601815023 0.798635510 1.327045e+00 54 0.587785252 0.809016994 1.376382e+00 55 0.573576436 0.819152044 1.428148e+00 56 0.559192903 0.829037573 1.482561e+00 57 0.544639035 0.838670568 1.539865e+00 58 0.529919264 0.848048096 1.600335e+00 59 0.515038075 0.857167301 1.664279e+00 60 0.500000000 0.866025404 1.732051e+00 61 0.484809620 0.874619707 1.804048e+00 62 0.469471563 0.882947593 1.880726e+00 63 0.453990500 0.891006524 1.962611e+00 64 0.438371147 0.898794046 2.050304e+00 65 0.422618262 0.906307787 2.144507e+00 66 0.406736643 0.913545458 2.246037e+00 67 0.390731128 0.920504853 2.355852e+00 68 0.374606593 0.927183855 2.475087e+00 69 0.358367950 0.933580426 2.605089e+00 70 0.342020143 0.939692621 2.747477e+00 71 0.325568154 0.945518576 2.904211e+00 72 0.309016994 0.951056516 3.077684e+00 73 0.292371705 0.956304756 3.270853e+00 74 0.275637356 0.961261696 3.487414e+00 75 0.258819045 0.965925826 3.732051e+00 76 0.241921896 0.970295726 4.010781e+00 77 0.224951054 0.974370065 4.331476e+00 78 0.207911691 0.978147601 4.704630e+00 79 0.190808995 0.981627183 5.144554e+00 80 0.173648178 0.984807753 5.671282e+00 81 0.156434465 0.987688341 6.313752e+00 82 0.139173101 0.990268069 7.115370e+00 83 0.121869343 0.992546152 8.144346e+00 84 0.104528463 0.994521895 9.514364e+00 85 0.087155743 0.996194698 1.143005e+01 86 0.069756474 0.997564050 1.430067e+01 87 0.052335956 0.998629535 1.908114e+01 88 0.034899497 0.999390827 2.863625e+01 89 0.017452406 0.999847695 5.728996e+01 90 0.000000000 1.000000000 1.633124e+16 Here's the print function I used to generate the above. print("{0:>5g} {1:.9f} {2:.9f} {3:e}".format( row, cos(theta), sin(theta),tan(theta)), end="\n", file= thefile) My module starts with: from __future__ import printfunction which is why I get to use this in 2.6 So why use Python as a calculator again? Because it's more like an old office machine with a tape, and that restores some of what was lost when lookup tables went out of style. I should do log10 next, using range with a step or something.... Also, the trig tape should probably be 0-360 but I didn't want to waste paper. :) Kirby

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for another lesson plan needing code
by kirby urner 18 Apr '10

18 Apr '10

""" Menu Fun by K. Urner Oregon Curriculum Network: DM Track Building up a small vocabulary of test modules will help you experiment with design patterns and syntax. You may wish to repurpose the code to be about something other then menu fun. Maybe save a snapshot with a different name. Fork off in a new direction. Possible grade level: DM(0) Suggested activities: * add the ability to create and retire trains * have a menu that dynamically lists trains * keep track of trains by number or name * after choosing a train, then prompt with status menu * add the option to pickle or otherwise store a train for future retreival. Exercises the following: string.Template, getattr, hasattr, setattr Illustrates: putting functions in a list and treating them as callables. """ from string import Template # to be more interesting """ this Train class might be instantiated multiple times. However in the code below, only a single instance is created when the mainloop is launched. """ class Train( object ): """ Only the one global train object in this module. Behaves likes C struct. No methods, just state. """ pass """ these functions check and/or change the status of the train, including whether it has a 'moving' attribute, added programmatically """ def start_train(thetrain): if hasattr( thetrain, 'moving' ): if thetrain.moving == True: print "The train is already moving." return thetrain.moving = True print "The train has started." def stop_train(thetrain): if hasattr( thetrain, 'moving' ): if thetrain.moving == False: print "The train has already stopped." else: thetrain.moving = False print "The train has stopped." else: print "The train has never moved." def add_car(thetrain): if getattr(thetrain, 'moving', False): print "Train moving, cannot add car." else: # Remains of an old error, left in for didactic purposes # print "DEBUG: ", getattr(thetrain, 'cars', 0) + 1 # thetrain.cars = setattr(thetrain, 'cars', getattr(thetrain, 'cars', 0) + 1) setattr(thetrain, 'cars', getattr(thetrain, 'cars', 0) + 1) print "%s has %s cars" % (thetrain.name, thetrain.cars) def remove_car(thetrain): if getattr(thetrain, 'moving', False): print "Train moving, cannot remove car." else: setattr(thetrain, 'cars', getattr(thetrain, 'cars', 1) - 1) if thetrain.cars <= 0: thetrain.cars = 0 print "%s has no cars" % thetrain.name else: print "%s has %s cars" % (thetrain.name, thetrain.cars) def end(thetrain): if hasattr(thetrain, 'moving'): print "The train is %s." % ( ['not moving','moving'][int(thetrain.moving)],) else: print 'The train never moved.' print "Logging out." mainmenu = Template(""" $name =========================== 1 - start train 2 - stop train 3 - add car 4 - remove car 0 - quit """) def menu_loop(): """ the only train is created here and persists only so long as the loop keeps looping. Consider adding menu options to store and retreive the train's state """ otrain = Train() # a train is born! otrain.name = "L&O Express" things_to_do = [start_train, stop_train, add_car, remove_car] # global functions while True: print mainmenu.substitute({'name':otrain.name}) menusel = raw_input("Choice?: ") if menusel in ['1','2','3','4']: sel = things_to_do[int(menusel) - 1] sel(otrain) elif menusel == '0': break else: print 'Choose 1,2 or 0' print "Quitting" end(otrain) # otrain goes out of scope here if __name__ == '__main__': menu_loop()

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intro to regular expressions
by kirby urner 15 Apr '10

15 Apr '10

Here's a module people could easily expand upon, staying with Jabberwocky as the target text. I'm by no means a master of the regexp. For example, I wanted to pick out all sentences with Jabberwock including those beginning and ending with quote marks (if present), i.e. keeping the quotes in the match. My current attempt loses the quote marks, keeping the enclosed sentence. One could imagine 20-30 more regexps, if not hundreds, populating this file. The doctest version could display expected output (except it gets kinda verbose (appended) -- maybe selected examples only...). Kirby === """ Playing with regular expressions... GPL 2010 4D Solutions This small suite of tests could easily be augmented with more elaborate ones, or simply variations on the theme. Consider this a workbench for test out your regexps. """ import re poem = """ 'Twas brillig, and the slithy toves Did gyre and gimble in the wabe; All mimsy were the borogoves, And the mome raths outgrabe. "Beware the Jabberwock, my son! The jaws that bite, the claws that catch! Beware the Jubjub bird, and shun The frumious Bandersnatch!" He took his vorpal sword in hand: Long time the manxome foe he sought- So rested he by the Tumtum tree, And stood awhile in thought. And as in uffish thought he stood, The Jabberwock, with eyes of flame, Came whiffling through the tulgey wood, And burbled as it came! One, two! One, two! and through and through The vorpal blade went snicker-snack! He left it dead, and with its head He went galumphing back. "And hast thou slain the Jabberwock? Come to my arms, my beamish boy! O frabjous day! Callooh! Callay!" He chortled in his joy. 'Twas brillig, and the slithy toves Did gyre and gimble in the wabe; All mimsy were the borogoves, And the mome raths outgrabe. """ def show_all(title, regexp, match_list): print "%s\n%s" % (title, len(title) * "=") print "regexp: %s\n" % regexp if match_list: for list_item in match_list: print list_item,'\n----' else: print "No Matches" print "\n\n" def test0(): """ Show the line of text in which Jabberwock appears, with ^ matching after \n, not just at the start of the string (the purpose of the MULTILINE flag). Given the word Jabberwock is not in the first line, there is no match without MULTILINE """ regexp = r"^.*Jabberwock.*$" p = re.compile(regexp, re.MULTILINE) m = p.findall(poem) show_all("Lines with Jabberwock", regexp, m) def test1(): """ Sentences in which Jabberwok appears, starting with a capital letter and ending with punctuation. The non-greedy .*? matches across \n because of DOTALL. After the first capitalized word, the matcher goes through any character that's not a terminating punctuation mark, through the string Jabberwock, and on to the terminus. """ regexp = r'[A-Z]\w+\b[^.!?"]+Jabberwock.*?[?!.]' # how to include outside quotes if present? p = re.compile(regexp, re.MULTILINE | re.DOTALL) m = p.findall(poem) show_all("Sentences with Jabberwock", regexp, m) def test2(): """ Find all strings enclosed in quotes (") that also and with an exclamation point. The *? makes * behave in a "non-greedy" manner, so the first satisfying pattern is considered a match. """ regexp = r'".*?!"' p = re.compile(regexp, re.MULTILINE | re.DOTALL) m = p.findall(poem) show_all("Exclamations", regexp, m) def test3(): """ Here we're looking for words starting with capital letters, then we're grabbing up to 3 characters on either side, including newlines if need be. The DOTALL is what picks up newlines. """ regexp = r'.{0,3}[A-Z]\w+\b.{0,3}' p = re.compile(regexp, re.MULTILINE | re.DOTALL) m = p.findall(poem) show_all("Capitals", regexp, m) def test4(): """ Here we're looking for words starting with capital letters, then we're grabbing up to 3 characters on either side, including newlines if need be. The DOTALL is what picks up newlines. """ regexp = r'.{0,3}[A-Z]\w+\b.{0,3}' p = re.compile(regexp, re.MULTILINE | re.DOTALL) m = p.findall(poem) show_all("Capitals", regexp, m) def alltests(): test0() test1() test2() test3() if __name__ == "__main__": alltests() === Lines with Jabberwock ===================== regexp: ^.*Jabberwock.*$ "Beware the Jabberwock, my son! ---- The Jabberwock, with eyes of flame, ---- "And hast thou slain the Jabberwock? ---- Sentences with Jabberwock ========================= regexp: [A-Z]\w+\b[^.!?"]+Jabberwock.*?[?!.] Beware the Jabberwock, my son! ---- And as in uffish thought he stood, The Jabberwock, with eyes of flame, Came whiffling through the tulgey wood, And burbled as it came! ---- And hast thou slain the Jabberwock? ---- Exclamations ============ regexp: ".*?!" "Beware the Jabberwock, my son! The jaws that bite, the claws that catch! Beware the Jubjub bird, and shun The frumious Bandersnatch!" ---- "And hast thou slain the Jabberwock? Come to my arms, my beamish boy! O frabjous day! Callooh! Callay!" ---- Capitals ======== regexp: .{0,3}[A-Z]\w+\b.{0,3} 'Twas br ---- es Did gy ---- e; All mi ---- s, And th ---- "Beware th ---- e Jabberwock, m ---- n! The ja ---- h! Beware th ---- e Jubjub bi ---- un The fr ---- us Bandersnatch!" ---- He to ---- d: Long ti ---- t- So re ---- he Tumtum tr ---- e, And st ---- . And as ---- d, The Ja ---- e, Came wh ---- d, And bu ---- ! One, t ---- o! One, t ---- gh The vo ---- k! He le ---- ad He we ---- "And ha ---- he Jabberwock? C ---- y! Callooh! C ---- !" He ch ---- 'Twas br ---- es Did gy ---- e; All mi ---- s, And th ----

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How do virtual 3D Second Life classrooms compare to WebEx for distance learning?
by chris＠seberino.org 15 Apr '10

15 Apr '10

I don't know if this educational topic is allowed on this but here goes... I do online math classes with video conferencing and a shared whiteboard. I'm trying to find out if doing virtual classes in Second Life with avatars offers any benefits. I've read up on this topic and the reports vary. Anyone have any experience going to a "class" in Second Life? cs

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Re: [Edu-sig] Why Python?
by David MacQuigg 15 Apr '10

15 Apr '10

Mark Engelberg wrote: >>> It's interesting to speculate whether there >>> will ever be another major improvement in programming, a step beyond >>> Python, or if Python will simply incorporate any good ideas that come >>> along (as it did with our @ syntax). I would bet on the latter. >>> > > Python has served me well for many years, but it is pretty poor at > handling concurrency, which is widely considered to be the hot issue > that future languages will need to solve. I am skeptical that Python > will be able to absorb these improvements into its existing > infrastructure. I would almost certainly bet that Python will be > superseded by superior languages, although possibly it has another 10 > or so more years of popularity to look forward to. > Good observation. I wasn't thinking of parallel computing at all. I can see a need for something very different in this realm. I'll stick with my original bet, however, if we limit our consideration to "mainstream" languages. I will bet that languages like Fortress, designed to deal with concurrency, will be used only by specialists, and that the majority just needing to process payroll records or program a website, will stick with whatever evolves from Python. Parallel programming is motivated by a need for speed. Already Python is fast enough for 99% of what we do, and that is without even taking the next logical step, merging C into Python in a way that puts no extra burden on those that don't need it. Add to that some extensions to Python that will make available at least the simplest techniques for parallel computing, and I'll bet the 99% majority will remain well served. That's not to say the 1% is unimportant. Here we will find brilliant programmers working on sophisticated techniques to break large problems into pieces that can be executed concurrently by hundreds of processors. Each problem is very different, and we may find programs for circuit simulation using very different techniques than programs for weather prediction. These programs will be run in an environment controlled by Python. The circuit designer or atmospheric scientist will not be concerned about the details of concurrency, as long as the result is fast and accurate. > Some food for thought: > http://research.sun.com/projects/plrg/Publications/ICFPAugust2009Steele.pdf > Excellent presentation of parallel programming. > The "Let's Add a Bunch of Numbers" slide is a great example of how > Python's style naturally encourages us to write code in exactly the > worst possible way from a concurrency standpoint. > Translating the slide to Python: > total = 0 > for i in range(1000000): > total = total+i > return total > > Programmers will eventually need to unlearn this kind of > process-one-at-a-time linear thinking. We will need programming > languages with lots of built-in rich tree-like structures, and a way > for specifying computations in a way that can be easily parallelized. > Lots of great experimentation is happening in this area -- it's only > a matter of time before the next language revolution. > The example above could be written in Fortress (or whatever is the new parallel language), and presented to the Python programmer as a simple function sum(X), replacing what is now written in C. The Python programmer need not even be aware of the upgrade. All he might notice is that summing a list of 10 million floats no longer takes 4 seconds, but appears to happen instantly. > In the meantime, I think that a strong emphasis on topics like trees, > recursion, immutable data structures, and divide-and-conquer > algorithms is a great way to future-proof our students and prepare > them for the "next big thing". > These are good topics for future professional programmers who might be in that elite 1%. I don't think other technical professionals will need to understand parallel programming, any more than they need to understand how modern pipeline processors execute instructions faster than if they were finishing one before starting the next. All bets are off if Wintel continues to successfully defend its version of Moore's law. Then we will need all those multicore processors just to balance our checkbooks. :>) -- Dave ************************************************************ * * David MacQuigg, PhD email: macquigg at ece.arizona.edu * * * Research Associate phone: USA 520-721-4583 * * * * ECE Department, University of Arizona * * * * 9320 East Mikelyn Lane * * * * http://purl.net/macquigg Tucson, Arizona 85710 * ************************************************************ *

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Those polyhedra again (ch.py)
by kirby urner 15 Apr '10

15 Apr '10

""" This version adds an instance variable self.keep that propagates though the scaling method to the next of kin. For example: >>> import ch >>> c = ch.Cube() >>> c.volume 3 >>> c.keep [] >>> bigc = c * 2 >>> bigc.volume 24 >>> c.keep.append("gem") >>> c.keep ['gem'] >>> bigc.keep ['gem'] >>> """ from math import sqrt as radical phi = (1 + radical(5))/2 class Poly( object): def __init__(self, edge = 1, edge_name = "edge", volume = 1, greekname = "Tetrahedron", platonic = True, dual = "Tetrahedron", keep=[]): self.edge = edge self.edge_name = edge_name self.volume = volume self.greekname = greekname self.platonic = platonic self.dual = dual self.keep = keep def scale(self, scalefactor): edge = self.edge * scalefactor # edge unbound to self volume = self.volume * pow(scalefactor, 3) # likewise volume # print("DEBUG: a star is born: a new %s" % self.__class__.__name__) return self.__class__(*(edge, self.edge_name, volume, self.greekname, self.platonic, self.dual, self.keep)) __mul__ = __rmul__ = scale # e.g. tetra = tetra * 3 def __repr__(self): return "Polyhedron of type %s (vol: %s)" % (self.greekname, self.volume) class Tetra( Poly ): pass class Cube( Poly ): def __init__(self, edge = 1, edge_name = "any face diagonal", volume = 3, greekname = "Cube", platonic=True, dual="Octahedron", keep=[]): super(Cube, self).__init__(*(edge, edge_name, volume, greekname, platonic, dual, keep)) class Octa( Poly ): def __init__(self, edge = 1, edge_name = "any edge", volume = 4, greekname = "Octahedron", platonic=True, dual="Cube", keep=[]): super(Octa, self).__init__(*(edge, edge_name, volume, greekname, platonic, dual, keep)) class R_Dodeca( Poly ): def __init__(self, edge = 1, edge_name = "any long face diagonal", volume = 6, greekname = "Rhombic Dodecahedron", platonic=False, dual="Cuboctahedron",keep=[]): super(R_Dodeca, self).__init__(*(edge, edge_name, volume, greekname, platonic, dual, keep)) class R_Triac( Poly ): def __init__(self, edge = radical(2)/2, edge_name = "any long face diagonal", volume = 7.5, greekname = "Rhombic Triacontahedron", platonic=False, dual="Icosidodecahedron", keep=[]): super(R_Triac, self).__init__(*(edge, edge_name, volume, greekname, platonic, dual, keep)) class Icosa ( Poly ): def __init__(self, edge = 1.0, edge_name = "any edge", volume = 5 * phi**2 * radical(2), greekname = "Icosahedron", platonic=True, dual="Pentagonal Dodecahedron", keep=[]): super(Icosa, self).__init__(*(edge, edge_name, volume, greekname, platonic, dual, keep)) class P_Dodeca ( Poly ): def __init__(self, edge = 1/phi, edge_name = "any edge", volume = (phi**2 + 1) * 3 * radical(2), greekname = "Pentagonal Dodecahedron", platonic=True, dual="Icosahedron", keep=[]): super(P_Dodeca, self).__init__(*(edge, edge_name, volume, greekname, platonic, dual)) class Cubocta ( Poly ): def __init__(self, edge = 1, edge_name = "any edge", volume = 20, greekname = "Cuboctahedron", platonic=False, dual = "Rhombic Dodecahedron", keep=[]): super(Cubocta, self).__init__(*(edge, edge_name, volume, greekname, platonic, dual)) def test1(): c = Cube() print "First shape: %s" % c print "Dual: %s Platonic: %s" % (c.dual, c.platonic) d = P_Dodeca() print "Second shape: %s" % d print "Dual: %s Platonic: %s" % (d.dual, d.platonic) def test2(): print "\n\nVolumes Table\n=============" for shape in (Tetra(), Cube(), Octa(), R_Triac()*pow(2./3,1./3), R_Dodeca(), R_Triac(), P_Dodeca(), Icosa(), Cubocta()): poly = "{0} ({1} = {2:.4g})".format(shape.greekname, shape.edge_name, shape.edge) print "{0:<60}{1:>8.4g}".format(poly, shape.volume) def test3(): print "\n\nDuals Table\n==========" for shape in (Tetra(), Cube(), Octa(), R_Dodeca(), R_Triac(), P_Dodeca(), Icosa(), Cubocta()): print "{0:<30}{1}".format(shape.greekname+" *"[int(shape.platonic)], shape.dual) print "\n * = Platonic" if __name__ == "__main__": # test1() test2() test3()

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an OO example (another zoo.py)
by kirby urner 14 Apr '10

14 Apr '10

""" playing with polymorphism by Kirby Urner Portland, Oregon April, 2010 """ import re from random import choice class Animal(object): def __init__(self, name): self.name = name self.stomach = [] def eat(self, food): self.stomach.append(food) def poop(self): if len(self.stomach) > 0: return self.stomach.pop(0) # queue def noise(self, howmany): pass def __repr__(self): return "A %s named %s in location %s" % (self.__class__.__name__, self.name, id(self)) class Mammal(Animal): def __init__(self, name): self.blood = "warm" super(Mammal, self).__init__(name) class Reptile(Animal): def __init__(self, name): self.blood = "ambient" super(Reptile, self).__init__(name) class Monkey(Mammal): def noise(self, howmuch): noises= ["Hoot","Screech","Jabber"] return "! ".join([choice(noises) for i in range(howmuch)])+"! " class Dog(Mammal): def noise(self, numbarks): return numbarks * "Woof! " class Snake(Reptile): def noise(self, howmany): return "Hissss.. " * howmany def test1(): animal1 = Dog("Spot") animal2 = Monkey("Red Devil") animal3 = Snake("Barry") print animal1, "goes: \n", animal1.noise(3) print animal2, "goes: \n", animal2.noise(4) print animal2, "goes: \n", animal2.noise(1) print animal1, "blood ", animal1.blood print animal2, "blood ", animal2.blood print animal3, "blood ", animal3.blood if __name__== "__main__": test1()

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