How to Zip two lists of lists in Python?

Last Updated : 17 Dec, 2024

zip() function typically aggregates values from containers. However, there are cases where we need to merge multiple lists of lists. In this article, we will explore various efficient approaches to Zip two lists of lists in Python. List Comprehension provides a concise way to zip two lists of lists together, making the code more readable and often more efficient than using the zip() function with additional operations.

Example:

Python

l1 = [[1, 2], [3, 4], [5, 6]] l2=  [[7, 8], [9, 10], [11, 12]]   # Zipping list res = [(a, b) for a, b in zip(l1, l2)] print(res)

Output

[([1, 2], [7, 8]), ([3, 4], [9, 10]), ([5, 6], [11, 12])]

Explanation:

zip() function pairs corresponding sublists from l1 and l2.
Combines these pairs into a list of tuples.

Let’s explore more method to zip two list of list.

Table of Content

Using `itertools.zip_longest`

This method allows us to zip two lists of different lengths, padding the shorter list with a specified default value. This ensures that both lists are iterated over completely, even if they have unequal lengths.

Example:

Python

import itertools a= [[1, 2], [3, 4]] b= [[5, 6], [7, 8], [9, 10]]  #Zipping with padding res = list(itertools.zip_longest(a, b, fillvalue=[])) print(res)

Output

[([1, 2], [5, 6]), ([3, 4], [7, 8]), ([], [9, 10])]

Explanation:

zip_longest() pairs sublists, filling missing values with [].
list() converts the pairs into a list of tuples.

Using a Loop

This method uses a loop to iterate through corresponding sublists in two lists and concatenate them with the + operator. The concatenated sublists are then added to a result list, which is printed at the end.

Example:

Python

a = [[1, 3], [4, 5], [5, 6]] b = [[7, 9], [3, 2], [3, 10]] res = []  # Iterating and concatenating sublists for i in range(len(a)):     res.append(a[i] + b[i]) print(res)

Output

[[1, 3, 7, 9], [4, 5, 3, 2], [5, 6, 3, 10]]

Explantion:

Combines corresponding sublists from a and b.
Appends the combined sublists to res.

Using numpy

When we are dealing with large datasets, numpy is a great choice for efficiency. It is specifically optimized for large-scale array operations and can perform zipping faster than standard Python lists when the data is numeric.

Example:

Python

import numpy as np l1 = [[1, 2], [3, 4], [5, 6]] l2 = [[7, 8], [9, 10], [11, 12]]  # Convert lists to numpy arrays res = np.array([np.array([a, b]) for a, b in zip(l1, l2)]) print(res)

Output

[[[ 1  2]   [ 7  8]]   [[ 3  4]   [ 9 10]]   [[ 5  6]   [11 12]]]

Explanation:

Pairs and converts sublists from l1 and l2 into NumPy arrays.
Combines them into a 2D NumPy array.

Concatenate two list of lists Row-wise-Python

manjeet_04

Improve

Article Tags :

Practice Tags :

The task of concatenate two lists of lists row-wise, meaning we merge corresponding sublists into a single sublist. For example, given a = [[4, 3], [1, 2]] and b = [[7, 5], [9, 6]], we pair elements at the same index: [4, 3] from a is combined with [7, 5] from b, resulting in [4, 3, 7, 5], and [1, 2

3 min read

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 ParallelA simple approach to iterate over

2 min read

Merge Two Lists into List of Tuples - Python

The task of merging two lists into a list of tuples involves combining corresponding elements from both lists into paired tuples. For example, given two lists like a = [1, 2, 3] and b = ['a', 'b', 'c'], the goal is to merge them into a list of tuples, resulting in [(1, 'a'), (2, 'b'), (3, 'c')]. Usi

3 min read

Convert Set of Tuples to a List of Lists in Python

Sets and lists are two basic data structures in programming that have distinct uses. It is sometimes necessary to transform a collection of tuples into a list of lists. Each tuple is converted into a list throughout this procedure, and these lists are subsequently compiled into a single, bigger list

3 min read

How to Split Lists in Python?

Lists in Python are a powerful and versatile data structure. In many situations, we might need to split a list into smaller sublists for various operations such as processing data in chunks, grouping items or creating multiple lists from a single source. Let's explore different methods to split list

3 min read

How to compare two lists in Python?

In Python, there might be a situation where you might need to compare two lists which means checking if the lists are of the same length and if the elements of the lists are equal or not. Let us explore this with a simple example of comparing two lists. [GFGTABS] Python a = [1, 2, 3, 4, 5] b = [1, 2

3 min read

Convert List of Tuples To Multiple Lists in Python

When working with data in Python, it's common to encounter situations where we need to convert a list of tuples into separate lists. For example, if we have a list of tuples where each tuple represents a pair of related data points, we may want to split this into individual lists for easier processi

4 min read

Python - Convert a list into tuple of lists

When working with data structures in Python, there are times when we need to convert a list into a tuple of smaller lists. For example, given a list [1, 2, 3, 4, 5, 6], we may want to split it into a tuple of two lists like ([1, 2, 3], [4, 5, 6]). We will explore different methods to achieve this co

3 min read

Python | Split nested list into two lists

Given a nested 2D list, the task is to split the nested list into two lists such that the first list contains the first elements of each sublist and the second list contains the second element of each sublist. In this article, we will see how to split nested lists into two lists in Python. Python Sp

5 min read

Python | Convert list of tuples to list of list

Converting list of tuples to list of lists in Python is a task where each tuple is transformed into list while preserving its elements. This operation is commonly used when we need to modify or work with the data in list format instead of tuples. Using numpyNumPy makes it easy to convert a list of t

3 min read

How to Zip two lists of lists in Python?

Using itertools.zip_longest

Using a Loop

Using numpy

Similar Reads

Using `itertools.zip_longest`