Mailman 3 August 2007 - Edu-sig

Using IDLE with students
by Richard Guenther 22 Aug '07

22 Aug '07

Sorry if this is a bit simplistic: When teaching Python to beginners and using IDLE, it seems that one of the dangers would be to have them assigning variables in the interactive mode and then maybe using them in a script they're writing. Then, when they run the script, the variable is still in memory so the program works--for now. Or, as happened recently "raw_input" gets accidentally assigned to a string. Then, any programs that end with "raw_input("Press Enter to exit this program")" will cause an error, even though the program script itself is fine. Obviously quiting and reloading IDLE will take care of this, but I was wondering what else may trip up students using IDLE. Maybe it would be nice if IDLE had an option called "Run fresh" that would clear any variables first....just musing here. Thanks, Richard ____________________________________________________________________________________ Shape Yahoo! in your own image. Join our Network Research Panel today! http://surveylink.yahoo.com/gmrs/yahoo_panel_invite.asp?a=7

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Re: [Edu-sig] Using IDLE with students
by John Posner 22 Aug '07

22 Aug '07

> When teaching Python to beginners and using IDLE, it seems that one of > the dangers would be to have them assigning variables in the > interactive mode and then maybe using them in a script they're > writing. Then, when they run the script, the variable is still in > memory so the program works--for now. >> I run into this a lot, and I find that it's very very difficult to explain >> what's going on to kids who are just getting their feet wet. Not denying that RESTART vs. no-RESTART is an issue, but ... if you're going to use IDLE in no-RESTART mode, why not reinforce the functionality as a *feature*, not avoid it as a bug. The module window works more like a macro than a self-contained program. For example, a lesson might investigate the Fibonacci series like this: 1. In the interactive window, set up some initial conditions: >>> a=1 >>> b=1 >>> count=2 2. Develop the following command sequence, by trial-and-error in the interactive window, as the way to perform one Fibonacci iteration: >>> a,b = b,a+b >>> count = count+1 >>> print "Fibonacci term", count, "is", b >>> print "ratio is", 1.0*b/a During this trial-and-error process, it's very likely that the initial conditions will need to be reestablished a number of times. 3. Use the interactive window's command-repetition capability (move the cursor, then press Enter) to invoke the command sequence repeatedly, generating Fibonacci iterations. 4. Invoke "New Window" and transcribe the command sequence into the new module window: a,b = b,a+b count = count+1 print "Fibonacci term", count, "is", b print "ratio is", 1.0*b/a 5. (SLIGHT GOTCHA) You must save the contents of the new module window in a file. 6. Repeatedly invoke "Run Module", producing more iterations in the interactive window: >>> Fibonacci term 14 is 377 ratio is 1.61802575107 >>> Fibonacci term 15 is 610 ratio is 1.61803713528 >>> Fibonacci term 16 is 987 ratio is 1.61803278689 >>> Fibonacci term 17 is 1597 ratio is 1.61803444782 >>> Fibonacci term 18 is 2584 ratio is 1.6180338134 >>> Fibonacci term 19 is 4181 ratio is 1.61803405573 Each time you (click in the module window and) invoke "Run Module", the four lines of code run in the current context of the interactive window. And more: * Use this repeated invocation of code to motivate "for" and/or "while" loops. * Describe the Golden Mean and compare the (converging) computed ratios to the actual value. To compute the actual value, you must import the "math" module. Best to all, John

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Urner, K.: message digest (special to edu-sig)
by kirby urner 21 Aug '07

21 Aug '07

My OLPC writings have moved to Synergeo @ Yahoo, under ownership of Ken Brown, closer to Calgary, Canada, and tracking OLPC from the beginning: http://worldgame.blogspot.com/2007/02/meeting-on-hawthorne.html Pithy Python @ Math Forum, per usual, e.g.: http://mathforum.org/kb/message.jspa?messageID=5851530&tstart=0 Otherwise, lots about MVC (Model View Controller), with this blog view a good summary: http://worldgame.blogspot.com/2007/08/model-view-controller-mvc.html Kirby

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Size of browser/window in school computer labs
by Andre Roberge 20 Aug '07

20 Aug '07

Hi everyone, I got some feedback today from someone who was using a *much* smaller size monitor than what I normally use and, after testing, realized that Crunchy (as currently designed) assumes that the display is much bigger than 800x600. So my question is: what size monitor is used in *your* school/college/university's computer lab? André

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Fwd: Re: Using IDLE with students
by John Zelle 17 Aug '07

17 Aug '07

I think Richard intended this for the group. Unfortunately, due to socket issues on Windows, said patch has not yet been implemented. ---------- Forwarded Message ---------- Subject: Re: [Edu-sig] Using IDLE with students Date: Friday 17 August 2007 8:24 am From: Richard Guenther <heistooheavy(a)yahoo.com> To: John Zelle <john.zelle(a)wartburg.edu> I remember installing a patch when I couldn't get IDLE to restart on my Windows computer. Here's a discussion of said patch: http://mail.python.org/pipermail/patches/2006-July/020360.html ----- Original Message ---- From: John Zelle <john.zelle(a)wartburg.edu> To: Richard Guenther <heistooheavy(a)yahoo.com> Cc: edu-sig(a)python.org; Guenther_Richard(a)stvrain.k12.co.us Sent: Thursday, August 16, 2007 9:25:12 PM Subject: Re: [Edu-sig] Using IDLE with students <<snip>> Yeah, now you run into the problem that you can only have 1 IDLE process running at a time. I don't understand why IDLE uses a fixed port. --John <<snip>> _____________________________________________________________________________ _______ Take the Internet to Go: Yahoo!Go puts the Internet in your pocket: mail, news, photos & more. http://mobile.yahoo.com/go?refer=1GNXIC ------------------------------------------------------- -- John M. Zelle, Ph.D. Wartburg College Professor of Computer Science Waverly, IA john.zelle(a)wartburg.edu (319) 352-8360

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Re: [Edu-sig] Using IDLE with students
by Richard Guenther 16 Aug '07

16 Aug '07

Well, after some experimenting on my laptop (Running Ubuntu 7.0.4 with Python 2.5.1), I've narrowed it down to this: 1. If I start IDLE from usr/bin through the terminal , it appears to run in "normal" mode. 2. If I start with the icon from Gnome menu applications/programming/IDLE, it does NOT start in "normal" mode, but of course you can go into system/main menu/launcher properties (rt. click) and take the "-n" off. Any reason why that is the default, though? What I did was declare a variable in the shell mode, then run a simple script that attempted to print that variable without declaring it first. In "-n" mode it would print "Assigned in shell" or whatever I had assigned to it in the shell. In "regular" mode, though, it would raise a traceback error ("a" is not defined). What I find interesting, though, is that in both cases ("-n" and "normal") you are still able to access variables that have just run in a program after the program is done running. For instance, if I run a program that declares a="assigned in program", I can later print out that variable in shell mode. So I've worked several Python books and tutorials, written both functional programs and some OOP, and yet I find myself not real clear on what exactly IDLE is ... :-( Ah well, at least my ubuntu menu launches IDLE in "normal" mode now. :-) Richard ----- Original Message ---- From: John Zelle <john.zelle(a)wartburg.edu> To: edu-sig(a)python.org Cc: Richard Guenther <heistooheavy(a)yahoo.com> Sent: Wednesday, August 15, 2007 9:13:32 AM Subject: Re: [Edu-sig] Using IDLE with students On Wednesday 15 August 2007 9:04 am, Richard Guenther wrote: > Sorry if this is a bit simplistic: > > When teaching Python to beginners and using IDLE, it seems that one of the > dangers would be to have them assigning variables in the interactive mode > and then maybe using them in a script they're writing. Then, when they run > the script, the variable is still in memory so the program works--for now. > Or, as happened recently "raw_input" gets accidentally assigned to a > string. Then, any programs that end with "raw_input("Press Enter to exit > this program")" will cause an error, even though the program script itself > is fine. > > > Obviously quiting and reloading IDLE will take care of this, but I was > wondering what else may trip up students using IDLE. Maybe it would be > nice if IDLE had an option called "Run fresh" that would clear any > variables first....just musing here. Provided you start IDLE in the "normal" mode, running scripts should execute in a separate subprocess, so the kinds of interactions you describe here are not really a problem. When running in this mode, you can also do a "restart" under the shell menu, and this will get you a fresh interactive environment. The problem is that the default IDLE setup in some environments starts up IDLE with the -n switch that causes it to run without separate subprocesses for scripts. For example, under Windows, if you right-click on a Python program and then select "edit with IDLE" it will open in the no-subprocess mode. I always have my students create a shortcut to IDLE in their working directories and make sure it starts IDLE without the -n switch, and I emphasize starting IDLE and then loading programs. By the way, another thing that will really help is getting students in the habit of writing scripts as functions and then just calling the function. That way variables are local to the function/script regardless of how IDLE is running (still doesn't solve problems like reassigning built-in functions though). --John -- John M. Zelle, Ph.D. Wartburg College Professor of Computer Science Waverly, IA john.zelle(a)wartburg.edu (319) 352-8360 ____________________________________________________________________________________ Pinpoint customers who are looking for what you sell. http://searchmarketing.yahoo.com/

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Re: [Edu-sig] Using IDLE with students
by Andy Judkis 16 Aug '07

16 Aug '07

> When teaching Python to beginners and using IDLE, it seems that one of the > dangers would be to have them assigning variables in the interactive mode > and then maybe using them in a script they're writing. Then, when they > run > the script, the variable is still in memory so the program works--for now. I run into this a lot, and I find that it's very very difficult to explain what's going on to kids who are just getting their feet wet. > Provided you start IDLE in the "normal" mode, running scripts should > execute > in a separate subprocess, so the kinds of interactions you describe here > are > not really a problem. When running in this mode, you can also do a > "restart" > under the shell menu, and this will get you a fresh interactive > environment. > > The problem is that the default IDLE setup in some environments starts up > IDLE > with the -n switch that causes it to run without separate subprocesses for > scripts. For example, under Windows, if you right-click on a Python > program > and then select "edit with IDLE" it will open in the no-subprocess mode. I > always have my students create a shortcut to IDLE in their working > directories and make sure it starts IDLE without the -n switch, and I > emphasize starting IDLE and then loading programs. The problem that I run into is that the livewires graphics package doesn't behave properly unless the -n is used. Here's a link with some background: http://mail.python.org/pipermail/edu-sig/2005-November/005583.html I think I've run into other packages that also have problems but livewires is the one I'm sure about. This has been a real problem for me. Andy

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Re: [Edu-sig] Using IDLE with students
by Richard Guenther 16 Aug '07

16 Aug '07

First, thanks to Andy, John and Kirby for responding--I no longer feel alone with my concerns about the namespace issues. Is there somewhere I can read up on these issues (other than the link to the Edu-sig archives that Any mentioned)? Before I ask I usually search the net a lot, but I didn't find much documentation on using IDLE in an educational setting. It would be nice if there was a tutorial that would cover the "gotchas" and also give advice to people considering using IDLE.... Curious, Richard ----- Original Message ---- From: kirby urner <kirby.urner(a)gmail.com> To: Andy Judkis <ajudkis(a)verizon.net> Cc: edu-sig(a)python.org Sent: Thursday, August 16, 2007 8:44:52 AM Subject: Re: [Edu-sig] Using IDLE with students The subprocess idea is important I agree. Also, psychologically, we would like students to see putting code in a module as "canning for later" i.e. there's a strong prejudice against thinking of the current session namespace as containing anything vital to the operations of the module. Picturing emailing the code to a distant user who has never once booted Python is another mental exercise one might use. Kirby _______________________________________________ Edu-sig mailing list Edu-sig(a)python.org http://mail.python.org/mailman/listinfo/edu-sig ____________________________________________________________________________________ Be a better Heartthrob. Get better relationship answers from someone who knows. Yahoo! Answers - Check it out. http://answers.yahoo.com/dir/?link=list&sid=396545433

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Re: [Edu-sig] Using IDLE with students (Richard Guenther)
by Andy Judkis 16 Aug '07

16 Aug '07

To follow up on my post of a minute ago, turtle graphics is also screwed up unless you run with -n. . . - Andy

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spinning 'self'
by kirby urner 14 Aug '07

14 Aug '07

Python is remarkably liberal in its design, in that 'self' is not a keyword. You're free to use other names for this important place in memory. Yet there's still self-imposed discipline (another way of saying 'self discipline'), such that we tend to all use 'self' anyway, by convention (but Python-the-interpreter doesn't complain if we don't -- not likely to change). However, as Python teachers have widely remarked, this concept of 'self' is not easily communicated at first, given the OO paradigm is itself still coming into focus for some students. In the class definition, the 'self' is really a 'place holder' (akin to zero) i.e. it doesn't do any work, but keeps a place open, like a driver's seat waiting for a driver. When an *object* of said class is created, the self becomes specified, as a kind of *anchor*. And plumbing the depths of 'self' is easy: all you need is __dict__ (i.e. a self is basically another namespace, a concept already familiar from earlier discussions). Python-by-comic-book (including on the net) is an emerging genre, influenced by Head First, Dive Into, and For Dummies series. I'm storyboarding for comics (could be TV shows) in which ' this ', ' me ' and ' ghost ' each get a crack at occupying the ' self ' position. Each of these English options has its own logic and connotations. I especially like ' ghost ' because of its ' ghost in the shell ' connotations (a link to manga, the genre we're in).[1] As Python goes towards Unicode, other "non-Romanji" substitutes for ' self ' may suggest themselves. However (back to self-discipline) I think it's wise to stick to the guidelines and go with non-idiosyncratic forms. David Goodger was good on this in his 'Idiomatic Python' at OSCON 2007 [2]: If your object is an iterable (i.e. has a "duck face" (which is like being a "duck type" but sounds more like "interface")) then address as such, as in in 'for myvar in self.__dict__', and not using has_key() or some such more specialcase form. In this same spirit (aha! another one), we just go with 'self' at the end of the day. Kirby [1] http://www.imdb.com/title/tt0113568/ http://www.imdb.com/title/tt0347246/ (theme song choral sequences some of my all time favorites) [2] http://oscon07.icalico.org/talk/view/271 Also mentioned in my blogs: http://controlroom.blogspot.com/2007/07/idiomatic-python.html

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