Mailman 3 December 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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New graphics library (beta version)
by John Zelle 01 Jan '05

01 Jan '05

I managed to get a bit of time today to play around with some changes I've been thinking about for my graphics library. Basically, my goal has been to get it to work better with the new IDLE. This new version runs TK in a separate thread so that a graphics window will stay responsive even when experimenting interactively at the IDLE prompt. Unfortunately, I am unable to run Windows at the moment, so I don't know if this works on that platform. I would love it if some of you could try it out and let me know. Specifically, I'd like to know if it "plays well" with the IDLE shell. A word of warning, I have not yet tested this very thoroughly even under Linux; it should be considered early Beta code. I hope to have a colleague test it out in our CS 1 class this winter (I'm not teaching it). Please give this a try if you're interested. Any and all feedback is welcome. --John

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Learn to Program in Ten Years
by Arthur 30 Dec '04

30 Dec '04

Some reality from Peter Norvig: http://norvig.com/21-days.html Other finds from a day of lazy exploration (us Jews have time on Christmas): A nice file browser written entirely in Python/pygtk http://claw3.berlios.de/index.php?page=downloads.html which tempts me to make exploring pygtk as an alternative to tkinter a priority, In fact I started a bit. And - So that's probably what Prasan was driving at: Boost *does* have an automated code generation tool: Pyste http://www.boost.org/libs/python/pyste/index.html though I am not sure why that disqualifies Boost for his teaching purposes. VPython's Boost code looks quite hand-coded. For myself, Pyste might actually be sane way to start understanding extension writing with Boost. And non-Python (mostly) but very interesting for those of us who like to work with graphics/3d with some good numerics behind it: """ Lush is an object-oriented programming language designed for researchers, experimenters, and engineers interested in large-scale numerical and graphic applications. """ http://lush.sourceforge.net/index.html It is a Lisp-like dialect with an interactive shell, but can generate C code, and has developed interfaces to major multi-media libraries like openGL,SDL,ALSA. Been around a while, is mature. It is interpreted when given untyped variable information, and compiled when given typed variables. And works nicely with inline C code. Wouldn't that be nice if Python... Not totally off-topic in any case since it does have bindings to the Python C API. The demos are written for Python2.2. I actually got into getting them to run on Python2.3 (change LONG_LONG to PY_LONG_LONG (thank you Google) - but when it got to trying to fix error messages it was generating related to _PyObject_GC_UnTrack I threw in the towel. Especially since I am not sure where the Lush/Python link is supposed to get you. __ A little effort at sharing my finds of the day. I hope no one objects. Art

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More calculus in Python
by Kirby Urner 30 Dec '04

30 Dec '04

This is part of an exchange with math profs over on math-teach*, but I think is of relevance here, given all the Python. KU * http://www.mathforum.com/epigone/math-teach/ghyrturcrerl ============== >On Dec 26, 2004, at 4:01 PM, Kirby Urner wrote: > >> To recapitulate how we'll do some of the early calculus stuff using >> Python, the advantage of top-level functions is you can pass them as >> arguments to other functions. This mirrors the behavior of the >> derivative operator, which Spivak likes to symbolize as D. >> D(f) -> g, means you take a function, f, operate on it (D), and >> spit back another function, g. > >Kirby, > >You may want to check out so-called "automatic differentiation". The >underlying idea is this: We overload the symbols of ordinary algebra, >thus extending algebra to the collection of ordered pairs (u, u'), where >u is a function and u' its derivative: > >(u, u') + (v, v') := (u + v, u' + v'); > >(u, u') * (v, v') := (u * v, u' * v + u * v'), > >etc. > >We embed the reals in this system: the real number a --> (a, 0). > >The identity function (which we abusively write as "x") is embedded as x >--> (x, 1). > >Of course, this can all be hidden from the user if we wish. > >Let's suppose that we have told our computer how to extend addition and >multiplication as above, and that we've given it the image of the >identity function too. > >Note what happens. When the machine uses these definitions to calculate >the squaring function, we get > >(x, 1) * (x, 1) = (x * x, 1 * x + x * 1) = (x^2, 2 x). > >This happens for other things as well, so we don't need to give most of >the formal embeddings. With what we've already done, we're ready to do >polynomial calculus now. With a few more rules [sin x --> (sin x, >cosx), the quotient rule > >(u, u')/(v, v') = (u/v, (u' * v - u * v')/v^2), > >etc.] we can do all of elementary calculus. > Thanks Lou. A first take in Python: write a Pair class to store (u, du) and define the basic four operations, as you've defined them; write a Function class to define the same four ops with respect to generic functions. Even ordinary numbers will be considered functions which "return their own value." class Pair: """ A generic pair (f, f'), both Functions (below), and rules for the four basic ops w/r to Pairs """ def __init__(self, u, du): self.u = u self.du = du def __add__(self, other): return Pair(self.u + other.u, self.du + other.du) def __sub__(self, other): return Pair(self.u - other.u, self.du - other.du) def __mul__(self, other): return Pair(self.u * other.u, \ self.du * other.u + self.u * other.du) def __div__(self, other): return Pair(self.u/other.u, \ (self.du * other.u - self.u * other.du)/other.u**2) class Function: """ A generic wrapper for uni-variable functions, allowing them to be composed using the four operations """ def __init__(self, f): self.f = lambda x: f(x) def __add__(self, other): return Function(lambda x: self.f(x) + other.f(x)) def __sub__(self,other): return Function(lambda x: self.f(x) - other.f(x)) def __mul__(self,other): return Function(lambda x: self.f(x) * other.f(x)) def __div__(self,other): return Function(lambda x: self.f(x) / other.f(x)) def __call__(self,x): """call wrapped function with argument x, return result""" return self.f(x) Now we define the identity function, and unity, per your language game. >>> def ident(x): return x >>> id = Function(ident) # Function-wrapped identity function >>> def one(x): return 1 >>> unity = Function(one) # Function-wrapped one Now we define a Pair (ident, unity) corresponding to your (x, 1). >>> p1 = Pair(id, unity) Multiplying p1 * p1 should return a new pair such that newpair.u is a parabolic or 2nd powering function, and newpair.du is the derivative thereof. >>> newp = p1 * p1 >>> [newp.u(i) for i in range(-5,6)] [25, 16, 9, 4, 1, 0, 1, 4, 9, 16, 25] >>> [newp.du(i) for i in range(-5,6)] [-10, -8, -6, -4, -2, 0, 2, 4, 6, 8, 10] So far so good. Thanks for this brain teaser and opportunity to show off functional programming in Python. Kirby

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Re: RE: [Edu-sig] Software developers - diarists or novelists?
by ajsiegel＠optonline.net 29 Dec '04

29 Dec '04

Kirby - > > I find Sean McGrath's blog writings, digested on Planet Python > > > > Thanks Arthur. > > I like this one: > http://patricklogan.blogspot.com/2004/12/roi-of-optional-type- > annotations.html > > Echoes my own sentiments at: > http://mail.python.org/pipermail/edu-sig/2004-December/004292.html Luckily, I don't pretend to have a handle on the issues involved in this one. Though I find just trying to follow the discussion to be an education - lot's of crossreference to other languages, etc. It sounds like Guido has another tough call on his hands. Its not easy being green, for Kermit. Sometimes I suspect its not easy being Guido. Art

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Software developers - diarists or novelists?
by ajsiegel＠optonline.net 29 Dec '04

29 Dec '04

I find Sean McGrath's blog writings, digested on Planet Python http://www.planetpython.org/ consistently interesting. This recent episode I particularly like. http://seanmcgrath.blogspot.com/archives/2004_12_26_seanmcgrath_archive.htm… Art

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IDLE Instabilities Update
by John Zelle 28 Dec '04

28 Dec '04

For those of you who have been having trouble with IDLE hanging (especially under Windows), I think one nasty glitch has now been ironed out. I posted a bug report on the idle-dev list and got a very prompt and thorough reponse from Kurt Kaiser who is apparently responsible for much (most?) of the current subprocess communication code. It turns out that the problem I found was quite old and not in the subprocess code at all, but a fix has now been checked in. Kurt sent me a patch for the idlelib/PyShell.py file. I have applied it against versions 1.03 and 1.1 of IDLE sucessfully. If you are interested in using this patch before the next version of Python is released, I have put the patch and patched versions of PyShell.py here: http://mcsp.wartburg.edu/zelle/IDLE Kurt believes that IDLE is actually very stable now, and I suspect that a lot of the troubles people have been reporting are the result of this bug that was just squashed (at least the problems that I've noticed in our lab were). I'd encourage any of you who use IDLE to patch your PyShell.py files (or drop in my replacement) and continue using IDLE. There is one remaining known issue on Windows. Due to a quirk in the underlying Windows socket code, it is apparently possible to have multiple (partial) starts of IDLE running at the same time, all bound to the same socket. This is very bad :-). For the moment, you just need to be sure to only have one copy of IDLE running at a time. My standard operating procedure is to start IDLE first, and then just load whatever files I want to work on. I keep IDLE running for my entire session, and have not had any problems. I'd be interested in hearing any feedback on whether this patch has made IDLE more workable for any of you. Also, if you are still finding instabilities in IDLE, we should try hard to track them down. At least some of the IDLE developers are keenly interested in stability. If we can track problems down, I think they will get fixed in realtively short order. Oh, and if you are using my graphics library interactively in IDLE on Windows, the graphics window will be unresponsive any time IDLE is waiting for input. This is annoying, but I haven't had a chance to rework my library yet for the new IDLE (it will probably require multiple threads, another topic of recent interest on edu-sig :-). --John ps. I came into the "learn to program in 10 years" thread late, so I did not bother to post, although there was much there of interest to me. Just for the record: 1. I really, really like KDE. IMHO it's better than aqua (honest) so you can keep your macs; I'll run on the cheap hardware :-) 2. I have noodled around a bit with PyQT (really should be QTPy don't you think ;-), and it seems very nice. The OpenGL widget works as advertised, and you can design GUIs with the standard QTdeveloper tools and convert to Python boiler plate (or parse them dynamically) much like Glade for gtk. 3. There are no license problems at all with QT on any platform, as long as you are not developing commercially. On Windows, you do need to license the widgets for commercial development (it's free on Linux, not sure on Mac). 4. I also want to do some things where VPython is embedded in other apps (specifically a Stereo 3D presentation system). However, Vpython is just one of several packages that I'd like to use. I am probably going to sacrifice portability and use X Window's ability to manipulate other windows (ala a window manager or plugger). Hopefully, some work on this will happen this Spring. 5. Software patents are ludicrous. Mathematical theorems are not patentable, neither should algorithms be. Unfortunately, the USPO has gone so far up this wrong road that it's hard to see how we will extricate ourselves. Let's hope the EU does the right thing. All of us need to keep up the fight on this issue in any small way we can.

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Learn to Program in Ten Years
by ajsiegel＠optonline.net 28 Dec '04

28 Dec '04

Dave writes: >I've used gtk/pygtk quite a bit and gtkglext with pyopengl a little bit. >I suggest you take a look at glade for designing the interface along >with libglade for parsing it. You can find a number of >articles/tutorials about using it here (yes, one of them is by me and >discusses glade/libglade): Thanks for this tip. And there is this artcle as well, linked from the site you reference: http://primates.ximian.com/~sandino/python-glade/ I find it quite reassuring to see such recent dates on these kinds of articles. And am getting a bit excited about getting hands-on with all this. It's interesting to see that Hilaire Fernandes also wrote some articles on the subject of PyGTK/Glade. I know of him as a worthy competitor - the author of Dr. Geo (http://www.ofset.org/drgeo ) - and a moving force behind The Organization of for Free Software in Education and Teaching http://www.ofset.org/ I did not know of any interest/involvement he had directly with Python before this, however. And related to prior discussion, this CookBook recipe allows one to experiment with building PyGTK GUI components from the interactive prompt: http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/65109 There is another such python module out there providing this functionality, but I don't find it out the moment. I'll have to try doing VPython inetractively through this mechanism and see if it tells me anything. Art

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Re: Learn to Program in Ten Years
by John Miller 28 Dec '04

28 Dec '04

I just wanted to chime in with a quote from a recent spe announcement: http://groups-beta.google.com/group/comp.lang.python/browse_thread/ thread/d71e84bb54aa4d9d ''' - wxGlade: wxGlade is a GUI designer written in Python with the popular GUI toolkit wxPython, that helps you create wxWindows/wxPython user interfaces. As you can guess by the name, its model is Glade, the famous GTK+/GNOME GUI builder, with which wxGlade shares the philosophy and the look & feel (but not a line of code). For more info: http://wxglade.sourceforge.net ''' This doesn't directly address the issue of which gui toolkit to actually use, but might help someone who decided on wxWidgets. John Miller On Dec 26, 2004, Dave Reed <drlinux(a)columbus.rr.com> wrote: > On Sunday 26 December 2004 16:35, Arthur wrote: >>> I just took a look at the PyGTK 2.0 Tutorial >>> http://www.pygtk.org/pygtk2tutorial/index.html >>> >>> Very encouraging to see that much documentation spelled out in a >>> usable >>> format. >>> > > (snip) > > I've used gtk/pygtk quite a bit and gtkglext with pyopengl a little > bit. > I suggest you take a look at glade for designing the interface along > with libglade for parsing it. You can find a number of > articles/tutorials about using it here (yes, one of them is by me and > discusses glade/libglade): > > http://www.pygtk.org/articles.html > > I've also found the C documentation for gtk is very easy to use when > programming in Python. It is very easy to translate the C functions > that take a gtk widget as the first parameter into a method of the > specificied pygtk widget. > > I've used it on Linux/Solaris, Windows XP and Mac OS X and it works > fine > on all of them. If I was coding for Windows only, I'd probably pick a > different widget set, but since I have little interest in programming > for Windows right now, I think glade/gtk is a great combination. > > Dave >

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Re: [Edu-sig] Learn to Program in Ten Years
by Laura Creighton 27 Dec '04

27 Dec '04

In a message of Sun, 26 Dec 2004 19:10:57 PST, "Kirby Urner" writes: <many good things> >That being said, I'm not against keeping some things secret or under wraps, >until ready for prime time. I still believe in wrapping presents, letting >things cook, season and so on. Immature technologies abound. The patent >office is overflowing with ideas that went nowhere (some deservedly). One thing that is not that well understood is that the patent system destroys the business models of those companies that rely on trade secrets as well as those that rely on openness. If your whole strategy is based on 'I know how to do this, you don't, and I'm not telling' then a patent infringement lawsuit is disastrous for you. It is nearly impossible to prove that you are not infringing without revealing what it is that you are doing. Plus some companies launch lawsuits they are convinced they will loose. They figure it is worth it to keep their competitors busy in court. This is less of a problem places where loser pays winner's attorney's fees, but not unheard of there. <snip> >Like, we have all we need to make the world a >better place for everyone, and yet here we are, screwing up, day after day. >Too slow. Let's pick up the pace here, shall we? Well said. Laura > >Kirby >

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