[Edu-sig] Cards n stuff...

[Kirby Urner]

At 01:34 PM 03/14/2001 -0500, you wrote:
>Thanks Kirby!
>
>This was really helpful.  The one line I would change is:
>
>  ranks  =  ['Ace']+map(str,range(2,11))+['Jack','Queen','King']

You could go:

ranks = ['Ace'] + [str(x) for x in range(2,11)] + ['Jack','Queen','King']

>I haven't discussed map at all yet, and actually don't plan to.
>

I think because of list comprehension syntax (as above), 'map'
and 'little lambda' are even less necessary than before.  

I really like the power of list comprehension, and think 
it makes sense to teach it e.g.:

  >>> def f(x):  return x*x

  >>> [f(x) for x in range(5)]  # successive 2nd powers
  [0, 1, 4, 9, 16]

and 

  >>> [f(x) for x in range(5) if x%2==0] # even 2nd powers only
  [0, 4, 16]

In a 'math through programming' context, it'll be combined
with 'zip' to create coordinate pairs, e.g.:

  >>> zip(range(5),[f(x) for x in range(5)])
  [(0, 0), (1, 1), (2, 4), (3, 9), (4, 16)]

This starts to become graphable, with appropriate methods in
the background.

>In using Python to teach, simplicity takes on even more importance
>than it usually has (and it is always important ;-)
>

Yes, I understand.  Usually you'll have a few students who 
want to tackle some of the more 'advanced' syntax, so having
exercises set aside for them makes some sense too.

>Python is such a wonderful language for teaching precisely
>because it "fits your brain".   In the case of students new
>to computing, "fitting their brains" means minimizing the number of
>previous concepts needed to understand a new concept.
>

Yes.

Also, though, it's great to start with kids without a lot of
preconceptions.  They can start fresh, taking OO concepts for
granted (no paradigm shift required).  

For example, the idea that 'map' distributes a function across 
a sequence of inputs sort of fits our mental picture of a conveyor 
belt, with someone squeezing frosting on each cupcake as it goes 
by, or whatever it is:

  >>> def add_frosting(thing): return thing + " with frosting"

  >>> map(add_frosting, ['cupcake']*5)
  ['cupcake with frosting', 'cupcake with frosting', 'cupcake with frosting', 
  'cupcake with frosting', 'cupcake with frosting']

Once you've got some hooks to visuals or well-known models, then 
these 'fancy' Pythonic expressions take on a more mundane appearance.  

map(str,range(10)) simply 'waves the magic wand' over a list 
0...9, where the 'wand', in this case, isn't add_frosting, but 
the 'convert to string' function str().  I know you know this -- 
just trying to imagine how I'd explain it to someone with no clue.

>In truth, what is good for new learners is good in general,
>only more so.
>
>Thanks again for your help!
>
>jeff

I've sent you a number more since then.  You probably won't 
want to use stuff like:

ranks = eval( '{' + 
            ','.join(["'%s':%s" % x for x in
               zip(['Ace'] +
                   [str(x) for x in range(2,11)] +
                   ['Jack','Queen','King'],
                   range(1,15))]) 
            + '}' )

But if your class is up for such a dictionary (using 'spelled out' 
rank to look up corresponding integer value), a more loopy 
initialization would be:
  
   def mkrankdict():
	j = 1
	dict = {}
	for i in ['Ace','2','3','4','5','6','7','8','9','10',
		  'Jack','Queen','King']:
	   dict[i]=j
	   j = j+1
	return dict

    ranks = mkrankdict()

  >>> ranks = mkranddict()
  >>> ranks
  {'8': 8, '9': 9, '6': 6, '7': 7, 'Jack': 11, '5': 5, '2': 2, 
  '3': 3, 'Queen': 12, 'King': 13, 'Ace': 1, '4': 4, '10': 10}

That'll be easier to read for a lot of us.  It'd be fun to show
these side-by-side, as two ways of getting the same result.

Kirby