Tuesday, November 12, 2013

Jef Raskin / Python Intersections

At the Homebrew Computer Club Reunion, I learned that there's the possibility of Jef Raskin's human interface ideas as realized in the Canon Cat will become available to a wider audience through an emulation project at archive.org. I'm not certain, but I believe that it's the TOSEC project.

Further, when looking this up today, I learned that Jef was using Python himself to implement his interface concepts. Unfortunately, raskincenter.org is gone today, the inhabited url by a camper. I'm sure the work is out there somewhere, but presently I'd have more interest in what Aza Raskin is up to, as he seems to be doing a fine job of carrying on.

Tuesday, January 29, 2013

Python for Android

I installed SL4A (Scripting Layer for Android) and Python for Android on my new Android Phone last night, and I've got to say this makes my phone the neatest portable device I've had since my HP 200LX.

The 200LX was basically an IBM PC-XT that fit in your pocket. It was a clamshell that ran a ROM version of DOS that was even capable of running early versions of Windows if you really, really wanted. My interest was more in running full DOS IDE packages like Turbo Pascal, Modula-2, Turbo C/C++, FORTH, etc. It also had a spreadsheet (Lotus 1-2-3) on ROM, ran dBase and the Clipper compiler well, and a host of other things. I kept one with me for over 10 years, long past its day, because I couldn't find anything comparable that I could carry with me as well and do so much with. There's nothing like being able to whip out a machine with a decent compiler on it while your wife is in the fitting rooms at the mall.

Well now I've got Python on my Android phone. This was my second try.

A False Start
Initially, I did a search on the Play Store. There I found something called QTPython+ that was a free download with at least a couple of positive reviews. Well, I couldn't figure out what it was up to. Its programs don't use normal Python I/O, and so far as I could tell (following the in-app link to the dev website), it's not that well documented. I'm clearly missing something, but it didn't work out for me.

Then, while paging idly through a copy of Android Development with Eclipse, I saw a mention in a later chapter about Python and other scripting languages. I got my phone and went out to the SL4A site right away, book in one hand, Android phone in the other.

The SL4A Install
For those that haven't been through it yet, it's not difficult to do the install, but it's not what you'll be used to from Google Play, or the Amazon App Store, either. At the SL4A site, you'll download and install the latest version of SL4A, which more or less is the support layer for the scripting language. I downloaded sl4a_r6.apk, which would be the R6 version of it. By itself, it doesn't get you much. I think you can get a command line with it.

The next step is to get the Python installer from the Python for Android site. I pulled one marked for R6, Python_for_Android_R6.apk. This is Python 2.6.2, there's another package for Python 3.

Either way, when you install that and start it up you'll get a menu asking whether you want to "Install". This seems confusing (at least it did to me late last night) as you'll ask yourself "Isn't that what I just did?" Actually, you've installed the installer. Click install and wait a few moments while it goes out and gets the other packages you need for a working Python install.

After that, you'll start the app from the SL4A icon. There you'll see a list of the example Python modules the bundle comes with. There are some good examples of starter Android apps there. But you don't have to do things the "Android Way" if you don't wish...

Command Line Junkie
You can also edit your own command-line/text-console Python programs. My first go was an off-the-top-of-my-head version of Guess.py from Invent Your Own Computer Games with Python (the textbook I'm using to start students off with Python in class this year.)

It had to be modded a bit for Python 2, of course, but it worked like a charm.

What fun!

The Source Code (as if you care) ;)
from random import randint
print 'I am thinking of a number between 1 and 20.'
print 'Try to guess it in 6 guesses or less.'

guesses = 0
guess = 0

while guesses<6:
    print 'Your guess? ',
    guess = int(raw_input())
    guesses = guesses + 1

    if guessnum:
        print 'Too high.'

    if guess==num:

if guess==num:
    print 'You got it in ',
    print guesses,
    print ' guesses!'

if guess!=num:
    print 'Too bad, the number was ',
    print num

Sunday, January 27, 2013

Yet Another Look at Graphics and Sound on Python


The more I look at it, the more I think the turtle module may be my answer for the graphics I need in the classroom. To recap, the basic ability I need from graphic in a classroom programming language is basic drawing and sprites. Cell or tile based graphics would be a big plus. In the non-python arena, Greenfoot pretty well has this covered for Java. It includes nice features like collision detection and distance determination as well.

Python's turtles can pretty well be treated as sprites. It's possible to have multiple simultaneous turtles in the current python versions. They can also be given unique appearances. It seems that the ability to use an image is there, but the documentation I've seen makes it look like a reserved feature. I'll have to look more into that.

Repurposing things like this always introduces an extra layer of complexity in the classroom. Students start to feel jerked around if you go and teach them that something is one thing, then start using it to do something else that doesn't follow from the first. In this case, perceiving the turtle as an indicator of where the drawing focus is when using turtle graphics, to forcing it into use as a free-moving entity that has various game behaviors we've associated with it.

It's not insurmountable, in this case, but it is more of a shift in thinking than a dedicated sprite class that aren't turtles by nature (perhaps a parent class of the turtle?)

In this case it's not a big deal, but in the classroom when little shifts like this start piling up one on another it gets harder to for the students to keep things straight and commit them to long term memory.

Another disadvantage of turtle graphics is that I pretty well have to develop my own material for class. I don't have a nice, pre-written book like Invent Your Own Computer Games with Python to draw on. That book is pretty much what let me bring python into my classroom. Using turtle graphics means that I have to write my own lessons using that module.


I still don't have a good answer for sound. The platform-independent library for sound in python has been taken out of the standard library. Sound is an important part of interacting with the computer for my students. When we've had teams developing video games using Greenfoot and Java in the past, it's not been unusual for the teams to have one of four students spend most of their time creating sounds and music for the games.

Python doesn't even have the ability to go "beep" without a platform-dependent library being added to the core package, as far as I can tell. That's pretty pathetic, what with it being so far to this side of 1983 and all. There are days when I wish the classroom was still filled with 8-bit computers. This is one of the reasons why.

So now, the ability to make sounds is the main thing missing from python so far as my use in class is concerned. I can still use Pygame for that, or have the students call platform-dependent system commands to produce sound.

Wednesday, January 9, 2013

Invent with Python Version Dependencies

I was able to take some time in class today to work on figuring out version dependencies in the programs in Invent Your Own Computer Games in Python. I started with the obvious in the early chapters, changes to print() and input() for Python 2.7.

Then I jumped forward to the chapters that use Pygame. I installed Pygame on the lab computer I was at, which was a Mac running Lion, and was pleased to have it function without having to install all the SDL libraries. Then I tried out the example programs from chapters 17-20 in Invent with Python.

All Clear
It turns out that these all worked fine, without any modification from the code in the book. Since they're mostly a smattering of python holding together a pygame program. ;)

That means I can go around to the lab computers, install Python 2.7 and Pygame, and have that ready for when the students get to the later chapters. I'll take a part of a class period to go over the differences between 3.x and 2.x, then set them loose.

Future Changes
Meanwhile, I'm going through the exercises in the earlier chapters. In the future, I'll start the class with Python 2.7 and have them use the programs with the minimum modifications necessary to work with 2.7. That way the material in the book will still be as close as possible to the example code.

I'll also be providing the students with a page on our class website linking to the specific versions of Python and Pygame we're using in class for the different possible platforms they have at home.

Monday, January 7, 2013

Started Python in Class Today

Today my middle school (7-8th grade) classes started Python with the Sweigart book. Everything went well for all students. Had to show one where to find '*' on the keyboard and another how to edit a file, but that's expected.

I have to write up some turtle graphics exercises before they get to the Pygame-based content, now.

I may try using Pygame with Python 2.7 on the Mac. I've been encouraged to do so, so if time permits, I'll try it myself then pick a student or two to be trailblazers for the rest.

Sunday, September 30, 2012

Python Again This Year

Python went well enough in the classroom last school year that I'll be using it again this year. Last year we had to leave aside graphics programming because of problems with getting a working graphics library on Mac with Python 3 (Pygame, specifically. There are folks working on its problems.) But the students had a lot of fun even with the text programs from Invent Your Own Computer Programs with Python and their own variations on them. So that's enough to make Python worthwhile in class.

We'll be doing the same, and if Pygame works, we'll be adding that as well. Frankly, dealing with version differences between Python 3.x and 2.x in class is something that I don't feel would be productive, so if we don't have a Pygame that works with Python 3 on our Macs in the school's lab, I won't be going to Python 2.x to get it. We'll move on to something else. For middle school, we'll probably continue with more text programs and have fun with formatting and such. For the high school classes, we'll move over to Greenfoot with Java to do a video game project. In the past, my high school students have dealt with the differences between Python to Java without much trouble. The middle school students who have outside experience with programming are similarly capable, but those who haven't or don't do any sort of programming or scripting outside of class struggle with the changes, so it's best just to avoid the change over at that level.

Prior to Python, the students will have had experience with HTML and CSS. Which presents another opportunity for output that's more interesting than simple console text--Python-generated HTML/CSS code. I've found HTML and CSS to be a good introduction to a lot of the concepts of programming, so it's often the first thing we do along those lines.

Finally, I can't say enough about how great a resource Al Sweigart's book is for my classes. It's a great introduction to programming, no matter the language, and Python makes a good starting language in spite of the "formatting as syntax" issues. It makes a great 21st century version of the great beginners' BASIC books of the 70s and 80s.

Here's hoping the Pygame/graphics issues will get resolved. If not, I need to take another look and see if the turtle graphics package is included in Python or will work with minimal effort on my part. If so, then I can prepare some lessons of my own using it to pick up where the text section of the Sweigart book leaves off.

Wednesday, February 29, 2012

Python 2, Python 3, and Pygame

I've been using Al Sweigart's excellent book as the core of a beginning programming curriculum for middle school students for the past four weeks. So far, it's going great.

But there have been some problems.

First, I was originally intending to use the version of Python already installed on our new Mac Minis. It's a version of Python 2.7, perfectly adequate for new programmers with no interest in which version of a language they're using. That would save me the trouble of doing 14 installs of a different version of Python.

But the book uses Python 3. I had looked at several possible books for the class, and hadn't entirely cottoned on to the fact this one had the exercises in Python 3. So I had a choice of trying to have the students see the differences between 2 and 3 on their own from the very first, before they have any idea what they're up to, rewriting the programs for the installed version of Python, or installing Python 3.

I decided to install Python 3.

Later, the book uses the pygame library to give Python graphics and sound capabilities. Unfortunately, there's no distribution package of pygame for Python 3 on Macintosh, only Windows (and possibly some of the Linux distros.)

So I tried to install pygame for 2.7. At least by the time my students get to chapter 17 in the Invent Your Own Computer Games with Python, I believe I'll be able to discuss the 2 vs. 3 syntax differences with them. Hopefully they'll be able to translate on their own. I expect to be doing Python 2 rewrites of the programs myself for next year's classes (unless a working pygame package appears for Python 3 on OS X Lion in the meanwhile).

It took me quite a few tries and a fair bit of my limited class prep time to find a combination of Python and Pygame that works on our school's lab computers. I discuss the details of that on my other blog. But I found a combo that appears to work today (pygame imports, and the first graphics program from the book runs.) I have installed it on 3 out of 14 computers so far, hopefully I'll have time to get it everywhere before the students reach that chapter.

Ass it is, I had already had to spend significant amounts of time developing alternatives to using the rest of the book after Chapter 16. My plan was to shift to turtle graphics, which appear to be bundled with Python 3.2 regardless of platform.

A Bit of a Rant

Frankly, as much as python has worked well for my students so far, if I had known the time and trouble I'd be running into I would never have even started using Python in class. There is no good Python solution here, everything is no better than a 9/10s solution.

Python, by itself, is pretty darn good. The current features in the standard distribution include graphics without requiring any external package installs on all 3 platforms I've run it on: Mac OS X, both 10.6 and 10.7, Win7, and Ubuntu 9.04 and 9.10. It's turtle graphics, but for the needs of my new programmers that fits the bill. I'd like to see standard sound support across platforms. Really, anything that supposes itself to be a general purpose language on this side of AmigaBASIC should be expected to support graphics and sound as standard features. Preferably without a ton of boilerplate. Here's hoping future Python versions can manage this.

The change in the print statement between Python 2 and 3 is maddening. The rationalizations aren't especially convincing to me, at least with respect to breaking backward compatibility and requiring silliness like "end=''" to suppress newlines. What great new ability has been gained for this cost? Nothing that's convinced me of the value yet. I expect this was discussed in PEPs somewhere. Parens, OK, I can possibly see adding those if it does something for added functionality (orthagonality with functions is not a convincing argument, to me.) But failing to provide a simple means of suppressing a newline like the earlier trailing comma, while going to a parametric assignment...that certainly appears well out of line with Python's apparent philosophy.

Now, pygame. No 3.X distributable for OS X? On what's touted as so wonderfully multi-platform? And it's not as if we're talking about a new version of Python that we need to just wait a week or two to get a binary for platform X ready. But Windows gets first class treatment. Mac OS? Not so much. Great multi-platform commitment, there.

I'm not at home to suggestions of compiling my own, I'm afraid. I could, for myself. But the world has a lot of machines that aren't just my own development system. The OS and hardware in our school's lab differs to what I run on my own systems. I haven't the time or desire to set up one of the school's systems as a dev box for porting software, then porting what claims to be a highly popular multi-platform package to the school's computers. Especially when they are a very popular hardware/OS mix already. I shouldn't be expected to put a large commitment of time and energy into getting this working at a point when I don't even know if it has any value to me yet.

And that still doesn't get me a package for Python 3, just for 32/64-bit, unless I move files by hand or make my own installer. While I'm a newcomer to python, for the most part, myself.

Good, but Not Quite Ready for Prime Time

That all said, I think I and my students will get plenty of value out of Python, pygame, and Al's book. But the price of entry for the package deal was too high. And we've still got this Python 2/3 version switch problem sitting in front of us, which I hope isn't going to turn into another big problem, but stay a little problem--though one that still needlessly eats up our limited class time with explanations of syntax differences rather than real new material.

Frankly, I couldn't possibly recommend doing this to others teaching at this level, as things stand at present. Things that would change this:

  • A book of the character and caliber of Al's that relies on no external package installs, just a current version of Python. Or,

  • An unambiguous install of Python and a matching compatible version of pygame, plus a book with matching code for that version in the exercises. Preferably as a single bundle installed all at once.

Edit: I've read PEP 3105 now. I still don't agree with breaking backward compatibility, as opposed to adding the function and deprecating the statement syntax. I also think there's reason for a simpler newline suppression syntax than the end parameter. Not every Python programmer is going to share the viewpoint of a python-dev wonk. ;) Some of them just want something simple that does the basics (print a string, suppress linefeed as needed--that's all.) In this case, the extended usage has broken the basic usage.

Addt'l edit: Reading "Python Regrets" now. The example syntax there of write() and writeln() would do the trick, from my teacher's standpoint. While I'm aware that redundancy is not a Python value, I think adding write() and writeln() to 3.x while keeping but deprecating the print statement for the term of one major version would have been a better approach (drop print when 4 comes.) Possibly limit print by rolling it back to a more limited version that doesn't allow redirection during 3, if the clock could be rolled back. Obviously at this point it's somewhat too late for that.