[PYTHON MATRIX-SIG] New Tutorial / Some Questions

[David Ascher]

Given that I'm starting a course on Python on Tuesday for a bunch of
neural net folks, I had to take a good hard look at the Numeric package.  
Jim H. has gotten more mail from me than he probably wanted.  The good
thing is that I didn't see myself teaching them about a feature that had
no documentation. So, I started a more detailed tutorial than that Jim
shipped in 0.33.  I aimed it at people who have very little python
experience, and no prior experience w/ matlab, basis, yorick or anything
like it (i.e.  undergraduates =).  It's obviously too basic for the
folks in this SIG, but I'd appreciate it if you could give it a
once-over and make sure I'm not lying outright.

It's available at http://maigret.cog.brown.edu/python/arraytut.html
for now.  It is very much under construction (I haven't explained rubber
indices and pseudo indices, for example, mostly because I'm not sure I 
understand them yet).

I came up with a few questions in the process.  Some have gone to jim
h. and hinsen, but I thought I'd spread the load:

1. I can't seem to find the counterpart to the toFile() method.

   I've tried just the array constructor w/ a file object, which I
   thought might work, but I get:

	>>> a
	0 0 1
	0 0 0
	1 2 3
	>>> f = open('myarray', 'w')
	>>> a.toFile(f)
	>>> 	f.close()
	>>> 	f = open('myarray', 'r')
	>>> b = array(f)
	>>> b

	Traceback (innermost last):
	  File "<stdin>", line 1, in ?
	  File "/usr/local/lib/python/numeric/Numeric.py", line 37, in
	arrayToString
	    items_per_line = a.shape[-1]
	IndexError: tuple index out of range

2. The choose() and take() methods are a little fuzzy for me.  Can
   someone give me a description of what they do, and more useful even
   examples of why they're useful?

3. Shouldn't typecodes look more like real types than strings, sort of
   like exceptions?  

	>>> b.typecode()
	'l'
   vs.
	>>> b.typecode()
	LongInteger  or whatever.

That's all for now.  Let me know what you think of the tutorial.

--david


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