[Edu-sig] Re: ..., closures, ... other weirdness

[Kirby Urner]

> Of course this method returns a string instead of printing the message.
> If you want to print the message you need to, def anon(x):
> because print is not a valid lambda expression (why?, I don't know):

Yes, right.

Plus you'll also need to define anon if you want your closure to consist of
more than one line of code (li'l lambda is just for one-liners).

> Closures are cool,
> Thanks,
> Jeff Sandys

Here's something else I learned about Python recently.  This is weird,
non-idiomatic stuff:  a pseudo-generator (of sorts) using function
attributes:

 >>> def weird():
         '''List consecutive Fibonacci numbers per each call'''
	   weird.x, weird.y = weird.y, weird.x + weird.y
	   return weird.x

 >>> weird.x = 1
 >>> weird.y = 1

 >>> for i in range(8): print weird(),

 1 2 3 5 8 13 21 34

But wait, there's more:

You can wrap this function with iter(callable, sentinel) to make it an
iterable:

 >>> weird.x = 1
 >>> weird.y = 1

 >>> wi = iter(weird,89)

 >>> for i in wi:  print i,

 1 2 3 5 8 13 21 34 55

So I guess in Python 2.4 we'll be able to go:

 >>> weird.x = 1
 >>> weird.y = 1
 >>> wi = reversed(iter(weird,89))
 >>> for i in wi:  print i,

 55 34 21 13 8 5 3 2 1

And now, to round out this little detour into arcane Python, let's make
weird() self-initializing, i.e. we don't want to have to assign weird.x and
weird.y before first use:

 >>> def weird(x=1,y=1):	
         '''List consecutive Fibonacci numbers per each call'''
         try:     weird.x
         except:	weird.x = x
	   try:     weird.y
	   except:  weird.y = y
	   weird.x, weird.y = weird.y, weird.x + weird.y
	   return weird.x

 >>> wi = iter(weird,89)   # note:  no "initialization" of weird needed

 >>> for i in wi:  print i,

 1 2 3 5 8 13 21 34 55

Weird.

Kirby