Multiply two lists element-wise in Python

Multiply two lists element-wise in Python #

To multiply two lists element-wise:

1. Use the zip function to get an iterable of tuples with the corresponding items.
2. Use a list comprehension to iterate over the iterable.
3. On each iteration, multiply the values in the current tuple.

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list_1 = [1, 2, 3]
list_2 = [4, 5, 6]

# 👇️ [(1, 4), (2, 5), (3, 6)]
print(list(zip(list_1, list_2)))

result = [x * y for x, y in zip(list_1, list_2)]

print(result)  # 👉️ [4, 10, 18]

The zip function iterates over several iterables in parallel and produces tuples with an item from each iterable.

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list_1 = [1, 2, 3]
list_2 = [4, 5, 6]

# 👇️ [(1, 4), (2, 5), (3, 6)]
print(list(zip(list_1, list_2)))

You can imagine that the zip() function iterates over the lists, taking 1 item from each.

The last step is to use a list comprehension to iterate over the zip object and multiply the values in each tuple.

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list_1 = [1, 2, 3]
list_2 = [4, 5, 6]

# 👇️ [(1, 4), (2, 5), (3, 6)]
print(list(zip(list_1, list_2)))

result = [x * y for x, y in zip(list_1, list_2)]

print(result)  # 👉️ [4, 10, 18]

On each iteration, we unpack the values from the tuple and use the multiplication * operator to multiply them.

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a, b = (2, 5)

print(a * b) # 👉️ 10

You can also use this approach to multiply more than two lists element-wise.

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list_1 = [1, 2, 3]
list_2 = [4, 5, 6]
list_3 = [7, 8, 9]

# 👇️ [(1, 4, 7), (2, 5, 8), (3, 6, 9)]
print(list(zip(list_1, list_2, list_3)))

result = [x * y * z for x, y, z in zip(list_1, list_2, list_3)]

print(result)  # 👉️ [28, 80, 162]

Alternatively, you can use the map() function.

To multiply two lists element-wise:

1. Use the map() function to call the mul() function with the two lists.
2. Use the list() class to convert the map object to a list.

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from operator import mul

list_1 = [1, 2, 3]
list_2 = [4, 5, 6]

result = list(map(mul, list_1, list_2))

print(result)  # 👉️ [4, 10, 18]

The map() function takes a function and an iterable as arguments and calls the function with each item of the iterable.

The mul function from the operator module is the same as a * b.

The map function returns a map object, so we had to use the list() class to convert the result to a list.