How to Split a List of Tuples into Two Separate Lists in Python – 4 Simple Methods

Problem

A fan in a Python community asked how to split a list of tuples like

[("a", 1), ("a", 2), ("a", 3), ("b", 1), ("b", 2), ("b", 3), ("c", 1), ("c", 2), ("c", 3)]

into two separate lists, one containing the first elements and the other containing the second elements.

Method 1 – Simple Loop

Iterate over the original list and append each component to its own list.

# coding:utf-8
letter_list = []
num_list = []
list1 = [('a',1),('a',2),('a',3),('b',1),('b',2),('b',3),('c',1),('c',2),('c',3)]
for i in list1:
    letter_list.append(i[0])
    num_list.append(i[1])
print(letter_list)
print(num_list)

Method 2 – Zip Unpacking

Use zip(*list1) to transpose the list of tuples.

list1 = [('a',1),('a',2),('a',3),('b',1),('b',2),('b',3),('c',1),('c',2),('c',3)]
list_result = tuple(zip(*list1))
letter_list = list(list_result[0])
num_list = list(list_result[1])
print(letter_list)
print(num_list)

A more concise form:

letter_list, num_list = zip(*list1)
print(letter_list)
print(num_list)

Method 3 – pandas

Convert the list of tuples into a DataFrame and extract each column as a list.

import pandas as pd
list1 = [('a',1),('a',2),('a',3),('b',1),('b',2),('b',3),('c',1),('c',2),('c',3)]
df = pd.DataFrame(list1)
print(df[0].tolist())
print(df[1].tolist())

Method 4 – numpy

Transform the list into a NumPy array and transpose it.

import numpy as np
list1 = [('a',1),('a',2),('a',3),('b',1),('b',2),('b',3),('c',1),('c',2),('c',3)]
letter_list, num_list = np.array(list1).T.tolist()
print(letter_list)
print(num_list)

Conclusion

All four approaches correctly separate the original list into two lists; choose the one that best matches your project's dependencies and readability preferences.