[Tutor] Re: List Comprehensions again [an example with filter()]

[dman]

On Sun, Jan 27, 2002 at 10:50:03PM -0500, Erik Price wrote:

| On Friday, January 25, 2002, at 10:19  PM, Danny Yoo wrote:
 
| Is using the three hashes a standard way of marking up example code in 
| Python?  I see it a lot on this list, and was wondering if it was 
| specific to the language or just a convention of this list.

Danny's convention.  Anything that is intuitively obvious works just
as well.  (I often use a bunch of tilde's, though usually I'm quoting
some config file or shell commands on a different list)

| >###
| >def endsWithS(word):
| >    return word[-1] == 's'
| >
| >for w in words:
| >    if endsWithS(w):
| >        print w
| >###
| 
| This is something I haven't seen before -- using an expression as the 
| return value of a function.

To be pedantic, you have seen an expression used in a return
statement.  Everything that isn't a statement (ie 'print' or 'import')
is an expression.  The only difference is that this expression is more
complicated than you've usually seen.

| I take it that this means "return boolean 
| value TRUE if the expression 'word[-1] == "s" ' ".  But I'm not sure.  
| It could be that instead, it returns the words that match?  If it did 
| that, then the second part, the "for" loop, wouldn't be necessary, so 
| drawing from context I am assuming that the former is true.

Yep.

| >You probably already feel comfortable passing around numbers and strings
| >to functions, but other functions?  If this is the first time you've 
| >seen
| >it, it will probably seem pretty darn weird at first, but it'll make 
| >sense
| >as you play with it.
| 
| You can create some pretty complicated constructs by passing functions 
| to other functions in PHP -- I find that it's sometimes easier to 
| conceptualize if I assign a function to a variable and then just pass 
| variables to functions.  But over time I'm sure I'll trade in this 
| clarity for convenience.

Sometimes it is clearer to give the function a new name.  It all
depends on the context -- what name does it already have and how do
you spell that name (ie is it a convoluted function call with complex
arguments or just a simple name?).

-D

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