How to iterate two lists in parallel - Python

Whether the lists are of equal or different lengths, we can use several techniques such as using the zip() function, enumerate() with indexing, or list comprehensions to efficiently iterate through multiple lists at once.

Using zip() to Iterate Two Lists in Parallel

A simple approach to iterate over two lists is by using zip() function in Python. we can combine two lists and iterate over them in parallel. It creates pairs of elements by matching elements from each list at the same index.

a = [4, 5, 3, 6, 2]
b= [7, 9, 10, 0]
# Iterate over each element in the combined lists (a + b)
for x, y in zip(a, b):
    print(x,y)

4 7
5 9
3 10
6 0

Here is a list of Various Methods to Iterate two lists in Parallel.

Using For Loop with range()

Apart from zip(), we can iterate two lists parallel if we use For Loop along with range. When using range(), we can iterate based on the indices of both lists, provided we ensure that we handle the case where the lists have different lengths.

a = [4, 5, 3, 6, 2]
b = [7, 9, 10, 0, 8]
# Use range() to iterate over the shortest 
# list's length to avoid index out of range error
for i in range(min(len(a), len(b))):
    print(a[i], " ", b[i])  

4   7
5   9
3   10
6   0

Using enumerate()

enumerate() function helps to iterate through each value in pair and helps to combine both index and the number.

a = [4, 5, 3, 6, 2]
b = [7, 9, 10, 0, 3]
for n, f in  enumerate(a):
    print(f,"   ",b[n])

4     7
5     9
3     10
6     0
2     3

Note: When the lists are of different lengths, using enumerate() with indexing can lead to an IndexError if you try to access an index in the longer list that doesn’t exist in the shorter one.