[Baypiggies] Another Python koan: modifying a list

[Jason Culverhouse]

On Nov 15, 2011, at 7:59 PM, Brian Rue wrote:

> A variation on the same theme:
> 
> >>> args = ["1", "2", "3,4", "5,6,7"]
> >>> args
> ['1', '2', '3,4', '5,6,7']
> >>> sum((x.split(',') for x in args), [])
> ['1', '2', '3', '4', '5', '6', '7']

That's pretty clever, I never used sum that way, i.e. concatenating a string by using the list's + operator.

this is similar but without the "magic"

from itertools import chain
chain.from_iterable( x.split(',') for x in args)

Jason

> On Tue, Nov 15, 2011 at 7:52 PM, Damon McCormick <damonmc at gmail.com> wrote:
> Casey, 
> 
> What is the intent of the following line?
> 
>   x[i:i+1] = items
> 
> Namely, what is the purpose of blowing away item i of x every time you insert a new list of items into x?
> 
> Is it possible that you mean something more like the following?
> 
>   x.extend(items)
> 
> If so, you could just do this:
> 
>   for element in mylist:
>       items = element.split(',')
>       x.extend(items)
> 
> Or even this:
> 
>   x = [item for element in mylist for item in element.split(,)]
> 
> -Damon
> 
> 
> On Tue, Nov 15, 2011 at 7:35 PM, Casey Callendrello <c1 at caseyc.net> wrote:
> Howdy there,
> Another python puzzle for everyone. I've been trying to come up with a Pythonic (i.e. no index variable) way of solving this.
> 
> I have a list consisting of one or more independent arguments to a specific command-line option. Think ./foo.py -a 1 -a 15 -a 1203. Argparse handles this fine. However, a few of my users prefer to specify arguments separated by commas instead. This is a fairly reasonable on their part, as about half of the tools we use like it one way, and half prefer the other. I don't mind supporting both, and the input data can never have a comma otherwise.
> 
> So, is there another way to express this code? In reality, the number of arguments is very small, so duplicating the array is no big deal. I'm still interested in a cleaner solution :-)
> 
> i = 0
> while i < len(mylist):
>    items = mylist[i].split(',')
>    if len(items) > 1:
>        x[i:i+1] = items
>    i++
> 
> --Casey Callendrello
> 
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