Mailman 3 March 2001 - Edu-sig

introduction and more on Cards
by Bruce Cohen March 31, 2001

March 31, 2001

It looks like the time has come to join this list. The thread on Card classes is just what I am doing right now. I am a math teacher at Lowell High School in San Francisco. I have not taught programming since 1981, but I was asked to teach a C++ course this year. The one semester course is supposed to prepare students who want to take the 1 year AP computer science class next year. Despite the fact that the College Board uses C++ as the AP vehicle (until they switch to Java in 2003?), I don't think C++ is the place to begin. Through my connections with the Computer Graphics Lab at UCSF (where the new molecular modeling package is written in Python <http://www.cgl.ucsf.edu/chimera/>), I became aware of Python. The more I learn about Python, the more I am convinced that it is a wonderful environment for students. I too recently thought about using a deck of cards to introduce objects to my students. In fact, I really wanted this for myself. Having done a good deal of C programming in the early '80s and Lisp in the late '80s, I had a decent understanding of programming paradigms, but no experience with OOP. My Card, Deck, and Hand classes look similar to the ones I have just discovered in the archives of this SIG. My first thought is to have students build a simulation of the game of "war" (see the description at the end of this e-mail). The boring nature of the game makes it ripe for computer data collection. (See http://home.att.net/~dambrosia/programming/games/war/ and http://www-ugrad.cs.colorado.edu/~kelloggp/War/index.html) As a novice with respect to object oriented programming, I would appreciate reactions to these two ideas: 1) using __cmp__ to overload comparisons. e.g. class Card: def __init__(self, Suit="spades", Value="Ace"): self._suit = Suit self._value = Value def __repr__(self): return str(self._value)+" of "+self._suit def __cmp__(self,other): if values.index(self._value) < values.index(other._value): return -1 elif values.index(self._value) > values.index(other._value): return 1 else: return 0 2) using inheritance: My Card class is good for war. Another game may require a different ordering (e.g. suits come into play). A second Card class (say SuitCard) could be based on Card but have a different overloading of __cmp__ Thanks. -Bruce ----------------------------------------------------------- (from http://www-ugrad.cs.colorado.edu/~kelloggp/War/index.html) The Rules of War (from Hoyle's Book of Card Games) Primarily a two-player game, preferably for juveniles, with a fifty-two-card pack ranking A, K, Q, J, 10, 9, 8, 7, 6, 5, 4, 3, 2 with suits disregarded. Each is dealt twenty-six cards face down, and each turns his top card face up. The higher value takes the lower and the cards are placed face down beneath the winner's packet. This continues indefinitely, until one player has won all the other's cards. If two cards happen to be tied - as two tens - they are laid aside and go to the winner of the next turnup. The player who gathers in all the cards wins the game. As an added rule, after a tie, each player lays a card face down before turning up another; and these cards also go to the winner of the next turnup.

2 1

Re: [Edu-sig] [Python-Help] Certification (fwd)
by Alan Gauld March 30, 2001

March 30, 2001

>I want to start kids off with Python. It's the best language I won't argue with that... > Right now they start on Visual Basic, which is disgusting. But I would argue with that. VB is a far better language to teach in a controlled (ie classroom) environment than say Java or, worse still, C++. It's certainly not disgusting, modern VB has most of the things needed for teaching introductory programming. But Python is better because it takes you further before running out of steam. :-) >a Python certification program, that would be good >enough for the board of education. Sorry, can't help you there. I can't even get my employer to feel happy about Python, never mind an education authority! Alan G.

1 0

[Python-Help] Certification (fwd)
by Daniel Yoo March 29, 2001

March 29, 2001

Dear Waldo, I'll forward you message to the edu-sig folks for you; they're definitely the people you want to talk to about Python in education. I hope that they'll be able to help answer your questions on certification. Off the top of my head: Learning Tree offers a course in Python programming: http://www.learningtree.com/ http://www.learningtree.com/us/ilt/courses/430.htm and they seem to focus on certification a bit, so you might want to talk to them. I'll let the other edu-sig'ers give their insight to your question too... *grin* Good luck to you. ---------- Forwarded message ---------- Date: Tue, 27 Mar 2001 17:50:14 -0500 From: Waldo Jaquith <waldo(a)waldo.net> To: help(a)python.org Subject: [Python-Help] Certification Folks, This probably isn't the best address to write to, but I'm really not interested in joining any mailing lists or anything right now. I'm a board member of the Information Technology Academy in Charlottesville, Virginia, USA. In a nutshell, we're working with local public schools to offer programming and computer-related education. Such things exist in schools now, but, frankly, they suck. I want to start kids off with Python. It's the best language to start on, or so people keep telling me. Right now they start on Visual Basic, which is disgusting. The problem is that you can't teach kids things in school unless you can prove that they've learned something. And to prove that they've learned something, you have to have a test. And to have a test, you have to be able to develop some sort of standards, or demonstrate that the standards exist. I'm not about to lobby the Commonwealth of Virginia to accept whatever Python standards that I might decide are good. On the other hand, if there were a commercial entity (non-profit or otherwise) that created a Python certification program, that would be good enough for the board of education. So my question is this: is there now, or will there soon be, such certification? I know such measurements are worthless to you and me, but they're essential to get Python in the classroom. Thanks for your time. Best, Waldo -- #define K(i)(x[i]^s[i+84])<< unsigned char x[5],y,z,s[2048];main(n){for(read(0,x,5);read(0,s,n=2048); write(1,s,n))if(s[y=s[13]%8+20]/16%4==1){int i=K(1)17^256+K(0)8,k=K(2)0, j=K(4)17^K(3)9^k*2-k%8^8,a=0,b=0,c=26;for(s[y]-=16;--c;i/=2,j/=2)a=a*2^1 &1,b=b*2^j&1;for(j=127;++j<n;c=z+c>y)a^=a>>14,a=a>>8^(y=a^a*8^a<<6)<<9, b=b>>8^(z=b^b/8^b>>4^b>>12)<<17,i=s[j],i="7Wo~'G_\216"[i&7]+2^"cr3sfw6v; *k+>/n."[i>>4]*2^i*257/8,s[j]=i^(i&i*2&34)*6^z+c+~y;}} Charles M. Hannum _______________________________________________ Python-Help maillist - Python-Help(a)python.org http://mail.python.org/mailman/listinfo/python-help

1 0

VPython/Tk visualization of residue classes
by Fred Yankowski March 27, 2001

March 27, 2001

I've been experimenting with ways to provide animated visualizations of simple mathematical concepts, and I'm fairly pleased with my latest effort which displays "residue classes" for different modulus values. The VPython/Tk program is available temporarily at <http://ontosys.com/src/residue2.py>. Note the Tk controller window that starts up along with the VPython display window. This program is motivated by the material in Chapter 2 of Conway and Guy's "The Book of Numbers" book. I think someone on this list recommended the book; it is a wonderful exposition of various patterns of numbers. -- Fred Yankowski fred(a)OntoSys.com tel: +1.630.879.1312 Principal Consultant www.OntoSys.com fax: +1.630.879.1370 OntoSys, Inc 38W242 Deerpath Rd, Batavia, IL 60510, USA

2 1

need help on python´s glob module
by Marcus Konermann March 27, 2001

March 27, 2001

Hallo ! i´m programming a project in my graduation with python an need help on python´s glob module. I don´t know the search routine, in which python searches through different files. For example: I let python search through the actuall directory with the command *.out (which specifies all files ending of ".out"). There are three files in the actuall directory named: ist.out, soll.out and rc.out. First, python takes the "rc.out" file, then the "ist.out" file and at last the "soll.out" file. So, it seems not to be an alphabetical order, in which python searches through this files. Please, can you tell me the search routine for python´s glob module ? Thanks a lot Grettings Marcus Konermann

3 2

Blender note
by Arthur_Siegel＠rsmi.com March 22, 2001

March 22, 2001

* Release of Blender 2.12. With 10 man-years of development added to Blender 2.0, we are excited to announce the latest release of Blender, including many new game engine, modeling and Python features! As a community member, you can download it March 16th, a few days before the official release at the Game Developers Conference (GDC). - http://www.blender.nl/showitem.php?id=160&page=1#release Powerful stuff, with a large and growing following - of mostly young hacker types, it seems. . Doing much with it is not on my own schedule, though. ART

2 3

RE: [Edu-sig] The Educational Robotics Platform
by Morris, Steve March 21, 2001

March 21, 2001

Kirby Urner wrote: > I wonder if it's cheating for a robot to have its "brains" in the > PC, with some kind of wireless connection to the servos. Perhaps > that's not any more cost effective. > > Wireless ethernet has certainly come down in price. Acually I missed your point the first time I read this so here is a better answer. Big brains in a host PC coupled with low level hands on the bits sensor/actuator control in the robot is a common model for robotics software development. Additionally a modern robot often has multiple computers on the robot connected with some kind of local area network. It is common for vision to be in one computer, looking at video data and extracting landmarks and object detail which then gets passed to some high level brain that makes decisions based on this info. Sometimes complicated details of the leg control of walking process (for legged robots) are delegated to a separate computer which is given high level objectives by the big brain. You still require a minimum threshold of compute power in the robot. (It has to be able to understand Ethernet for example.) Ethernet is also too slow for detailed control of the low level bits and bytes of sensors and actuators. This minimum level of compute power sets the low level price bar. Infrared is interesting because it can carry simple serial port data which makes it REALLY cheap. You just use standard TV remote IR parts and almost every embedded micro has a serial port built in. However infrared is even slower than Ethernet. To give you an idea, the inner loop of the LEGO RCX is some small number of thousandths of a second (I don't remember exactly but 2 milliseconds rings a bell.) Not much needs to be done in that inner loop but delays caused by other code will break the robot. The minimum low cost robotics processor is one that can do a couple of simple things every couple of milliseconds but also handle the high level decision making in the background. This low level stuff should be completely hidden from the programmer (in timer interrupt handlers etc) but the capability is necessary for the low level robot driver stuff. It is this mix of extremely frequent but low load processing responsiveness balanced with slower but more powerful and time consuming high level computation that defines the real-time programming problem. (That and the problem of many things happening in parallel.) It is this mix that Windows and out of the box Linux can't handle. The summary answer to your question is that high level processing that a host PC could do is not the hard part so offloading it doesn't save much if any money. On the other hand since a host CPU is often available (that's where you write the code) it is a valuable tool to increase what you can do with the robot. Using that host in conjunction with a remote link to the robot only increases the possibilities. It just doesn't solve the low cost minimum useful robotics platform problem.

1 0

A potential LEGO Python robotics connection.
by Morris, Steve March 21, 2001

March 21, 2001

There is a way to write LEGO robotics software in Python. The default firmware in the computer brick is a VM which hass immediate commands and downloadable software. On Windows LEGO provides a VXD (basically a software library) that does all the heavy lifting of interacting with the RCX computer. LEGO provides high quality documentation of how to use this VXD. A simple Python wrapper around this VXD makes all of the capapabilities of the machine available to Python running on the host. (The LEGO RCX has an infrared link to the PC.) This has already been implemented for many other Windows languages including C++, Visual Basic, Smalltalk, and Tcl to name a few. Someone may have even done it for Python already. These languages provide good examples of how to do it. The current language of choice for the RCX is called NQC (Not Quite C.) It is quite usable for teaching robotics, certainly much better than the graphical front end toy that LEGO delivers, but of course it is not Python so off topic for this list. NQC is basically a compiler that compiles to the native VM of the RCX. The reason it is Not Quite C is that the VM isn't powerful enough to support C. NQC is a C like language that efficiently lives within the restrictions of the RXC VM. Systems like LegOS and pbForth go one step further. They are firmware that replace the RCX VM completely. LegOS is C based and could theoretically support Pippy if it was small enough. The current state of the world of low end robotics is that platforms like the LEGO RCX are really too small and slow to do much and real platforms like PC/104 are too expensive and lack the basic infrastructure to glue high level languages to sensors and actuators. Moore's law is solving the PC/104 price problem and efforts like Jonathan's should solve the second. In five years robotics will be widely available for all levels of teaching. Today it is a path for the early adopter pioneers willing to do a lot of distracting (from the teaching point of view) nitty gritty work.

1 0

RE: [Edu-sig] The Educational Robotics Platform
by Morris, Steve March 21, 2001

March 21, 2001

> I wonder if it's cheating for a robot to have its "brains" in the > PC, with some kind of wireless connection to the servos. Perhaps > that's not any more cost effective. Using a PC is definitely not cheating and can be much cheaper if you use an existing PC. The down side is that an existing PC will usually have a real time unfriendly OS like Windows or standard Linux which makes it difficult to use cheaper sensors. Cheap simple sensors require very fast response time because a lot of the work is done in software. Workstation type operating systems think nothing of turning off the outside world for major fractions of a second, fast for a human but slow for reacting to physical events that a robot sees. This is one of those design goal problems with workstations. Just like workstation tools like Python assume that plenty of disk and RAM is available, workstation OS' assume that they can hog time at human perception rates. A lot of work has been done in the last couple of years to make Linux compatible with real-time requirements, for example RTLinux, which directly address the low level robotics response time requirements. This will make Linux the OS of choice in coming years, especially as the cost of Linux capable platforms comes down. We are sitting at the cusp. John Pennington's work is addressing this. > Wireless Ethernet has certainly come down in price. True but unfortunately not in power consumption. Power is a big issue for robots since they have to carry their power supply. The main reason you don't want to use a PC with cable is that it limits the robots mobility. However many interesting robotics applications don't require mobility. It is very common to do both, use a workstation for development and an autonomous computer in the application. This is again where Jonathan's work is interesting. Things like Pippy run on many platforms. Another interesting application of robotics hardware is physics experiments. Some robot sensors can detect wheel angle. This allows doing things like putting a robot on a ramp, letting it roll and measuring the wheel angle with time. From this data and measured wheel size speed and acceleration with time can be calculated. From there the acceleration due to gravity can be measured. A little vector calculation with ramp angle and the force of gravity is measured. Data reduction can me done in Python on the workstation although I prefer a spreadsheet for this. When I do data reduction in a computer language I copy and paste the results into the program using it to initialize an array. LEGO Mindstorms itself might be responsive enough to do this experiment, especially with a shallow ramp to slow things down. Robots and their gears and pulleys are good platforms for learming about mechanical advantage and simple machines. A vital part of robotics development is measuring the behavior of the robot and its sensors. This process of analyzing real world attributes should be a good teaching tool. Simpler measurements can be factored into a lesson plan. Things like how close does the light sensor have to be before it sees an object (by reflection. LEGO light sensors have built-in light source.) Are different surfaces detected at different distances, different colors, shiny vs. flat. How does this impact the robots algorithm. This interactive process of quantifying and understanding physical properties is obviously quite valuable. A robotics professional has to understand computers and software, electronics and mechanical engineering, leverage and transfer of energy, noise, friction losses and efficiency, algorithm development, sensors and actuators, working within external constraints etc. There is rich ground here for all kinds of learning experiences. If Jonathan can make the connection between Python and robots Python can have a major role to play.

1 0

RE: [Edu-sig] The Educational Robotics Platform
by Morris, Steve March 21, 2001

March 21, 2001

> Let me see if I understand you correctly. JavaVM fits in > smaller places > than Python because it was written tight from the start. > uController's > are often very small memory systems, 64k maybe. So you're > VM (and with > Python we use this term very loosely) has to fit in about > 32k or less. > Getting down that small is essential if you want to have a robot > price-tag of $100 or under - which would be, in your opinion, the > threshold to broadly introducing robots in the classroom. I didn't mean anything that specific. Mostly I was just rambling. I do think robotics teaching in the classroom is price sensitive. The lower the price the more it will be used. That doesn't mean there isn't value at other price points. It just means that there will be a lower level of acceptance. Here is a simplified price/performance analysis. I have skipped the lowest price (PIC etc.) solutions. LEGO already owns the middle low end. There is no point in competing there. Here the potential value add is in software. Nobody has got it right yet for this kind of application. Mindstorms graphical interface is a toy and LegOS/pbforth etc are too hard for the entry level user. Python would be ideal however you are unlikely to get Python into 32k of the LEGO bricks. The LEGO brick also suffers badly in communication back to the host which is required for serious development. Hacking the board to replace the unreliable IR with a real serial port would be a "Great Leap Forward" for this platform. The next price point is possibly 16 bit bus micros with a larger address space. Something based on the 68k with 1/2 meg of ram would easily fit Pippy and generally increase usability by an order of magnitude. A total system cost of less than $300 might be possible in this space. The Palm Pilot comes to mind in this category because it is the Pippy target. Its PowerBall micro is 68000 based. A Palm with I/O added (maybe a Handspring type I/O card) would be a powerful low end Robotics controller. It has good development tools (including Pippy) and is low power. The Palm has a Linux port also. The Palm was one of the original targets of embedded Linux. Ideally you want a smaller data bus (lower price) with some kind of extended addressing (beyond 64k) combined with a good C compiler, preferably gcc. (gcc gives you the ability to port things like Pippy.) You also want someone else to make the board in volume so this is a search for, not a make selection process. With your project (PC/104 based) you are talking about the next level which is machines that are 32/64 bit bus with multi megabyte address range but can still run stripped down real time Linux Kernels. This opens development choices substantially. I think it is worthwhile to work on this platform but the end price for hardware, motors and sensors will likely be in the $500-$700 price range which will restrict its target audience. This is the Cadillac of low end robotics machines but will definitely be the winner as prices come down. Working in this space you would have to be happy with lower initial acceptance. I like RTLinux as the OS of choice for this kind of platform for various reasons I don't need to address on this list (which is probably already getting annoyed with this level of detail on such a speculative project.) > Because Python was not written with such small memory environments in > mind, it is hard to retrofit it. You end up trying to > rewrite the core > so you can leave out things. (Pippy for example can get > down to about > 70k, if you chuck the parser/compiler, floating point, and some other > stuff.) You doubt that Python can get down to the 32k > requirements to > fit it on the cheap uProcessors. Yep.

4 3