How to Transpose a List of Lists in Python: Methods

A list is a data structure that stores multiple objects in a single variable. It is also mutable and creates ordered elements. If you want to transpose a list of lists in Python then this post is for you. In this tutorial, you will learn the various methods to Transpose a List of Lists in Python.

Methods to Transpose a List of Lists in Python

To transpose a list of lists in Python, you can use multiple methods. Below are the different approaches to find the transpose.

Method 1: Using Nested List Comprehension

You can use nested list comprehension to transpose the list of lists.

original_list = [[10, 20, 30], [40, 50, 60], [70, 80, 90]]

transposed_list = [[original_list[j][i] for j in range(len(original_list))] for i in range(len(original_list[0]))]

print(transposed_list)

Output

[[10, 40, 70], [20, 50, 80], [30, 60, 90]]

Method 2: Using the zip() function

You can use the built-in zip() function along with the unpacking operator (*) to transpose the list of lists. Use the below lines of code.

original_list = [[10, 20, 30], [40, 50, 60], [70, 80, 90]]

transposed_list = list(map(list, zip(*original_list)))

print(transposed_list)

Output

[[10, 40, 70], [20, 50, 80], [30, 60, 90]]

Method 3: Using the numpy library

If you have the Numpy library installed, you can use it to transpose the list of lists.

import numpy as np

original_list = [[10, 20, 30], [40, 50, 60], [70, 80, 90]]

transposed_list = np.transpose(original_list).tolist()

print(transposed_list)

Output

[[10, 40, 70], [20, 50, 80], [30, 60, 90]]

Method 4: Using a loop

You can also use a loop to transpose the list of lists.

original_list = [[10, 20, 30], [40, 50, 60], [70, 80, 90]]
transposed_list = []

for i in range(len(original_list[0])):
    transposed_row = []
    for j in range(len(original_list)):
        transposed_row.append(original_list[j][i])
    transposed_list.append(transposed_row)

print(transposed_list)

Output

[[10, 40, 70], [20, 50, 80], [30, 60, 90]]

Method 5: Using the pandas library

If you have the pandas library installed, you can use its DataFrame to transpose the list of lists.

import pandas as pd

original_list = [[10, 20, 30], [40, 50, 60], [70, 80, 90]]
df = pd.DataFrame(original_list)
transposed_list = df.transpose().values.tolist()

print(transposed_list)

Output

[[10, 40, 70], [20, 50, 80], [30, 60, 90]]

Conclusion

Many coders use Python List to store multiple variables in a single variable. In this tutorial you have learned how to transpose a list of lists in different methods like numpy, pandas, loop, nested list comprehension, etc You can use any method you want.