If you’re in a hurry, here’s the most Pythonic way to convert a nested tuple to a nested list:
The list comprehension statement
[list(x) for x in tuples] converts each tuple in
tuples to a list and stores the results in a list of lists.
But there’s more to it! Studying the different methods to achieve the same goal will make you a better coder.
So keep reading!
Method 1: List Comprehension + list()
Here’s a concrete example:
tuples = ((1, 2), (3, 4), (5, 6)) lists = [list(x) for x in tuples] print(lists) # [[1, 2], [3, 4], [5, 6]]
Try It Yourself:
This approach is simple and effective. List comprehension defines how to convert each tuple (
x in the example) to a new list element. As each list element is a new list, you use the constructor
list(x) to create a new list from the tuple
Example Three Elements per Tuple
If you have three elements per tuple, you can use the same approach with the conversion:
tuples = ((1, 2, 1), (3, 4, 3), (5, 6, 5)) lists = [list(x) for x in tuples] print(lists)
You can see the execution flow in the following interactive visualization (just click the “Next” button to see what’s happening in the code):
Example Varying Number of Tuple Elements
And if you have a varying number of elements per tuple, this approach still works beautifully:
tuples = ((1,), (3, 3), (5, 6, 5)) lists = [list(x) for x in tuples] print(lists) # [, [3, 3], [5, 6, 5]]
You see that an approach with list comprehension is the best way to convert a tuple of tuples to a list of lists.
But are there any alternatives?
Method 2: Use Asterisk and List Comprehension
A variant of the recommended way to convert a tuple of tuples to a list of lists is using list comprehension in combination with the unpacking asterisk operator
* like so:
[[*x] for x in tuples].
Here’s an example:
tuples = ((1,), (3, 3), (5, 6, 5)) lists = [[*x] for x in tuples] print(lists) # [, [3, 3], [5, 6, 5]]
The unpacking operator
[*x] takes all tuple elements from
x and “unpacks” them in the outer list container
[...]. For example, the expression
[*(5, 6, 5)] yields the list
[5, 6, 5].
Let’s have a look at a completely different approach to solve this problem:
Method 3: Map Function + list()
💡Side Note: Guido van Rossum, the creator of Python, didn’t like the
map() function as it’s less readable and less efficient than the list comprehension version (Method 1 in this tutorial). You can read about a detailed discussion on how exactly he argued on my blog article.
So, without further ado, here’s how you can convert a tuple of tuples into a list ot lists using the
tuples = ((1,), (2, 3, 4), (5, 6, 7, 8)) lists = list(map(list, tuples)) print(lists) # [, [2, 3, 4], [5, 6, 7, 8]]
Try it yourself:
Video tutorial on the
The first argument of the
map() function is the
list function name.
The result of the
map() function is an iterable too, so you need to convert it to a list before printing it to the shell because the default string representation of an iterable is not human-readable.
Method 4: Simple For Loop with append() and list()
To convert a tuple of tuples to a list of lists, a simple three-liner is to first initialize an empty “outer” list and store it in a variable. Then iterate over all tuples using a simple
for loop and convert each separately to a list and append each result to the outer list variable using the
list.append() builtin method in the loop body.
The following example does exactly that:
tuples = ((1,), (2, 3, 4), (5, 6, 7, 8)) lists =  for t in tuples: lists.append(list(t)) print(lists) # [, [2, 3, 4], [5, 6, 7, 8]]
Related Video Tutorial
Related Conversion Articles
- How to Convert a List of Lists to a List of Tuples
- How to Convert a List of Lists to a Pandas Dataframe
- How to Convert a List of Lists to a NumPy Array
- How to Convert a List of Lists to a Dictionary in Python
Where to Go From Here?
Enough theory. Let’s get some practice!
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While working as a researcher in distributed systems, Dr. Christian Mayer found his love for teaching computer science students.
To help students reach higher levels of Python success, he founded the programming education website Finxter.com. He’s author of the popular programming book Python One-Liners (NoStarch 2020), coauthor of the Coffee Break Python series of self-published books, computer science enthusiast, freelancer, and owner of one of the top 10 largest Python blogs worldwide.
His passions are writing, reading, and coding. But his greatest passion is to serve aspiring coders through Finxter and help them to boost their skills. You can join his free email academy here.