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Python Program to Iterate Through Two Lists in Parallel

In this example, you will learn to iterate through two lists in parallel.

To understand this example, you should have the knowledge of the following Python programming topics:


Example 1: Using zip (Python 3+)

list_1 = [1, 2, 3, 4]
list_2 = ['a', 'b', 'c']

for i, j in zip(list_1, list_2):
    print(i, j)

Output

1 a
2 b
3 c

The loop runs until the shorter list stops (unless other conditions are passed).


Example 2: Using itertools (Python 2+)

import itertools

list_1 = [1, 2, 3, 4]
list_2 = ['a', 'b', 'c']

# loop until the short loop stops
for i,j in itertools.izip(list_1,list_2):
    print i,j

print("\n")

# loop until the longer list stops
for i,j in itertools.izip_longest(list_1,list_2):
    print i,j

Output

1 a
2 b
3 c


1 a
2 b
3 c
4 None

izip_longest() lets the loop run until the longest list stops.

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