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pythonlistpython-2.7

Iterate every 2 elements from list at a time

Having list as , 

l = [1,2,3,4,5,6,7,8,9,0]

How can i iterate every two elements at a time ?

I am trying this , 

for v, w in zip(l[:-1],l[1:]):
    print [v, w]

and getting output is like , 

[1, 2]
[2, 3]
[3, 4]
[4, 5]
[5, 6]
[6, 7]
[7, 8]
[8, 9]
[9, 0]

Expected output is 

[1,2]
[3, 4]
[5, 6]
[7, 8]
[9,10]
Solution

  • You can use iter:

    >>> seq = [1,2,3,4,5,6,7,8,9,10]
>>> it = iter(seq)
>>> for x in it:
...     print (x, next(it))
...     
[1, 2]
[3, 4]
[5, 6]
[7, 8]
[9, 10]

    You can also use the grouper recipe from itertools:

    >>> from itertools import izip_longest
>>> def grouper(iterable, n, fillvalue=None):
...         "Collect data into fixed-length chunks or blocks"
...         # grouper('ABCDEFG', 3, 'x') --> ABC DEF Gxx
...         args = [iter(iterable)] * n
...         return izip_longest(fillvalue=fillvalue, *args)
... 
>>> for x, y in grouper(seq, 2):
...     print (x, y)
...     
[1, 2]
[3, 4]
[5, 6]
[7, 8]
[9, 10]