Source: 📖 Effective Python item 36

itertools.zip_longest

This variation of the zip function zips according to the length of the longest iterator provided, filling missing values with a placeholder value that can be passed in to the fillvalue parameter:

keys = ['one', 'two', 'three']
values = [1, 2]

normal = list(zip(keys, values))
print('normal zip: ', normal)

it = itertools.zip_longest(keys, values, fillvalue='nope')
longest = list(it)
print('zip_longest: ', longest)

>>>
normal zip: [('one', 1), ('two', 2)]
zip_longest: [('one', 1), ('two', 2), ('three', 'nope')]

See also:

• How zip works
• Use zip_longest as an alternative when necessary