Python program to split a list into two lists with alternating elements

Question

Can you make it more simple/elegant?

def zigzag(seq):
    \"\"\"Return two sequences with alternating elements from `seq`\"\"\"
    x, y = [], []
    p, q =          


        

Answer 1

def zigzag(seq):
    return seq[::2], seq[1::2]

Answer 2

I just wanted to clear something. Say you have a list

list1 = list(range(200))

you can do either :

## OPTION A ##
a = list1[1::2]
b = list1[0::2]

or

## OPTION B ##
a = list1[0:][::2] # even
b = list1[1:][::2] # odd

And get have alternative elements in variable a and b.

But OPTION A is twice as fast

Answer 3

If seq, as you say, is a list, then:

def zigzag(seq):
  return seq[::2], seq[1::2]

If seq is a totally generic iterable, such as possibly a generator:

def zigzag(seq):
  results = [], []
  for i, e in enumerate(seq):
    results[i%2].append(e)
  return results

Answer 4

This takes an iterator and returns two iterators:

import itertools
def zigzag(seq):
    t1,t2 = itertools.tee(seq)
    even = itertools.islice(t1,0,None,2)
    odd = itertools.islice(t2,1,None,2)
    return even,odd

If you prefer lists then you can return list(even),list(odd).