On Monday, August 26, 2002, at 03:06  AM, Danny Yoo wrote:

>  I think it's pretty good; have you had a chance to look at the sample
>  Chapter 1 yet?
> 
>      http://www.oreilly.com/catalog/pythoncook/chapter/index.html
> 
>  As a warning: I'm not a disinterested party in my endorsement.  *grin*

Well, in that first chapter, David Ascher's opening commentary includes 
the following quote, that I need help with:

"""
My favorite recent language features are list comprehensions and the new 
applicability of the * and ** tokens to function calls as well as to 
function definitions.  List comprehensions have clearly become wildly 
successful, if the authors of this volume are representative of the 
Python community at large, and have largely demoted the map and filter 
built-in functions.  Less powerful, but equally elegant, are * and **.  
Since Python 2.0, the oft-quoted recipe:

   def method(self, argument, *args, **kw):
     # Do something with argument
     apply(callable, args, kw)

can now be done much more elegantly as:

   def method(self, argument, *args, **kw):
     # Do something with argument
     callable(*args, *kw)

"""

This must be a new form of callable(), because in my copy of Python 
Essential Reference (for 2.1), callable() takes one parameter argument 
that is an object.

I understood what map() and filter() do, but why are list comprehensions 
better?  FWIW, I don't really know exactly what a list comprehension is, 
only that PER says that the following

   map(function, alist)

can be better written using list comprehension as

   [function(x) for x in alist]

-- why?


Thanks for any thoughts that anyone can contribute.


Erik



--
Erik Price

email: erikprice@[...].com
jabber: erikprice@[...].org


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