Code question

[Matimus]

On Apr 21, 12:05 pm, <jyoun... at kc.rr.com> wrote:
> I've been trying to figure out a way to combine lists similar to how zip() works.  The main
> difference though is I want to work with different length lists and combine them.  I came up with
> the example below, which returns a list like I'm wanting.  I'm assuming it's somewhat efficient
> (although I wonder if the lists were huge that the 'if' statement might slow things down?).
>
> If anyone has time, I was wondering if you could share your thoughts on whether this is an
> efficient way to do something like this, if it's horrible and slow, etc.
>
> Thanks!
>
> Jay
>
> # ----------------------------
>

>
> def combineLists(theLists):
>     cntList = len(theLists)
>     lenList = [len(x) for x in theLists]
>
>     maxList = max(lenList)
>
>     combinedList = []
>
>     for x in range(maxList):
>         for n in range(cntList):
>             if lenList[n] > x: combinedList.append(theLists[n][x])
>
>     print combinedList
>
> combineLists([a, b, c])
>
> # ----------------------------
>
> # --> ['a', '1', 'a1', 'b', '2', 'b2', 'c', 'c3', 'd4', 'e5']

I would probably do something like this:

>>> def combine(*seqs):
...    seqs = [iter(s) for s in seqs]
...    while seqs:
...       for g in seqs:
...          try:
...             yield g.next()
...          except StopIteration:
...             seqs.remove(g)
...
>>> a = 'abc'
>>> b = '12'
>>> c = 'a1 b2 c3 d4 e5'.split()
>>> list(combine(a,b,c))
['a', '1', 'a1', 'b', '2', 'b2', 'c', 'c3', 'd4', 'e5']

It has the advantage that it uses the generator protocol, so you can
pass in any type of sequence. It uses arbitrary arguments to make its
use closer to that of zip. It is also a generator, so it takes
advantage of lazy evaluation. Notice that there is never any checking
of length.

Matt