Implicit lists

[Christian Tismer]

Alex Martelli wrote:
> On Friday 31 January 2003 04:36 am, Christian Tismer wrote:
>    ...
> 
>>Besides th fact that I believe strings as sequences
>>should be deprecated, since nobody makes use of it,
> 
> 
> This is an overbid, IMHO: some (small) fraction of the time,
> say 10%, I'm quite happy that strings are sequences for 
> looping purposes; and far more often than that, for purposes
> of slicing, concatenation, repetition.  Deprecation can maybe
> be mooted for Python 3.0, of course, but no earlier.

Sorry, I didn't really express what I meant.
A reply from Guido first reminded me that
we of course need string slicing and indexing.
And then I realized that we are not seeking
for "sequenceness" or "stringness" at all.

What people really want to know is whether
"is this argument meant as a single argument
or is it a container of arguments".
That turns the overall question into
"is something a container"?

This still gives some ambiguities with multi-
purpose chamaeleans like the Numeric arrays,
but strings and array.array objects are very well
covered: They *are* sequences, but you don't
want them to be taken as argument collections,
since they are no containers.

Here the same, written in some bad Python style,
but as a builtin, it would do quite much
simplification for argument checking:

 >>> def iscontainer(obj):
... 	try:
... 		obj[0:0]   # is sequence
... 		try:
... 			buffer(obj)
... 			return False
... 		except:
... 			pass
... 		return True
... 	except:
... 		return False
...
 >>> iscontainer("")
0
 >>> iscontainer(1)
0
 >>> iscontainer(())
1

I'm (ab)using the fact that sequences which are
no containers usually support the buffer interface.

ciao - chris