How to iterate in pairs over a list with ODD cardinality in python-CodePudding

I want to iterate over a list pair-wise in Python, except the list has an odd number of elements.

I know if this list is even for item1,item2 in zip(alist[0::2],alist[1::2]) would work, but if the list is odd the loop breaks out before it processes the last item.

Is there any efficient way to handle this?

Example:

list a = (a,b,c,d,e,f,g)

Expected elements in each iteration:

(a,b)
(c,d)
(e,f)
(g,None) # or some other placeother value for the non-existent 2nd element of the pair

CodePudding user response：

You can use itertools.zip_longest:

from itertools import zip_longest


alist = ["a", "b", "c", "d", "e", "f", "g"]

for i in zip_longest(alist[0::2], alist[1::2]):
    print(i)

Prints:

('a', 'b')
('c', 'd')
('e', 'f')
('g', None)

CodePudding user response：

You can append None:

for item1,item2 in zip(alist[0::2],alist[1::2] [None]):
    ...