Last modified: Oct 30, 2024 By Alexander Williams

# Adding Each Element of Two Lists in Python

Adding elements of two lists in Python is common in data processing. Here’s how to efficiently add each element in one list to the corresponding element in another.

## Using zip() for Element-Wise Addition

`zip()`

allows us to pair elements from two lists by index, making it ideal for element-wise addition. Here’s a basic example:

```
list1 = [1, 2, 3]
list2 = [4, 5, 6]
sum_list = [a + b for a, b in zip(list1, list2)]
print(sum_list)
```

```
[5, 7, 9]
```

In this example, each element in `list1`

is added to the corresponding element in `list2`

. The result is a new list.

## Using List Comprehension

List comprehension offers a concise way to handle element-wise addition when lists are of the same length. It combines looping and addition into one line.

For more details, check out Loop Moves to Next Element in List in Python.

## Handling Lists of Different Lengths

If the lists are of unequal lengths, **using a padding method** like filling missing values with `0`

ensures all elements are accounted for:

```
from itertools import zip_longest
list1 = [1, 2, 3]
list2 = [4, 5]
sum_list = [a + b for a, b in zip_longest(list1, list2, fillvalue=0)]
print(sum_list)
```

```
[5, 7, 3]
```

In this case, the shorter list is padded with `0`

using `zip_longest()`

, allowing all elements to be added correctly.

## Using NumPy for Larger Lists

**NumPy** is ideal for mathematical operations on large lists or arrays. With `numpy.add()`

, you can add lists element-wise quickly:

```
import numpy as np
list1 = [1, 2, 3]
list2 = [4, 5, 6]
sum_list = np.add(list1, list2)
print(sum_list)
```

```
[5 7 9]
```

Using `np.add()`

is both efficient and concise for handling large data arrays. To learn more, see NumPy’s documentation.

## Conclusion

Python offers flexible ways to add elements of two lists, from `zip()`

for basic tasks to `NumPy`

for high-performance operations. Choose the method that suits your data size and requirements best.