foo.reverse() actually reverses the elements in the container. reversed() doesn't actually reverse anything, it merely returns an object that can be used to iterate over the container's elements in reverse order. If that's what you need, it's often faster than actually reversing the elements.
Top answer 1 of 8
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foo.reverse() actually reverses the elements in the container. reversed() doesn't actually reverse anything, it merely returns an object that can be used to iterate over the container's elements in reverse order. If that's what you need, it's often faster than actually reversing the elements.
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There seems to be a great difference. I really thought it's the other way round. Why is rearranging the values in a list faster than creating a new one from an iterator ?
from decorators import bench
_list = range(10 ** 6)
@ bench
def foo():
list(reversed(_list))
@ bench
def bar():
_list.reverse()
foo()
bar()
print foo.time
print bar.time
0.167278051376
0.0122621059418
Reddit
reddit.com › r/pythontips › [video] python's reverse() vs reversed() - how they differ
r/pythontips on Reddit: [Video] Python's reverse() Vs reversed() - How they differ
January 16, 2024 - On the flip side, reversed() is a function that returns a reversed iterator, allowing you to create a reversed version without altering the original list.
reversed vs [::-1]
Note that reversed() doesn't return a list, it returns an iterator. Your code snippets aren't equivalent. Should programmer choose carefully between slicing and reversed? Only if you have huge lists that take up gigabytes of memory. Just choose the one that expresses your intent more clearly. More on reddit.com
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June 24, 2014[Video] Python's reverse() Vs reversed() - How they differ
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January 16, 2024why reversed (list) is iteratorable but list.reverse() is not?
Basically because the reverse() function has a return type of None, it modifies the list in place. It's a call to a function, not to the list itself. Just like you couldn't do reversed_list = list.reverse(), because reversed_list would hold the value of None (But the list variable would still be reversed in-place). Where list[::-1] is a call to the list itself, with instructions on how to iterate through it. More on reddit.com
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August 26, 2024Why does [::1] reverse a string in Python?
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September 21, 2023Videos
Geek Python
geekpython.in › reverse-vs-reversed-in-python
Reverse Vs Reversed Function In Python - Comparison
January 17, 2024 - The reverse() function from Python List is used to reverse the elements in a List wjereas, Python reversed() function takes a sequence and returns the reversed iterator object.
GeeksforGeeks
geeksforgeeks.org › python › python-reversed-vs-1-which-one-is-faster
Python - reversed() VS [::-1] , Which one is faster? - GeeksforGeeks
July 15, 2025 - The format [a : b : c] in slicing states that from an inclusive to b exclusive, count in increments of c. In the above code, a and b are blank and c is -1. So it iterates the entire list counting from the last element to the first element resulting in a reversed list. ... # Python code to reverse a list using slicing # Original list original_list = [110, 220, 330, 440, 550] print('Original list:', original_list) # Reversing the list using slicing reversed_list = original_list[::-1] # Printing the reversed list elements print('Reversed list elements:') for element in reversed_list: print(element)
Medium
medium.com › @naqvishahwar120 › reverse-vs-reversed-in-python-9c210e3f125e
reverse() vs reversed() in Python - Shahwar Alam Naqvi - Medium
January 17, 2025 - reverse() vs reversed() in Python Python reverse() Mutating method : It modifies the original list Returns nothing, just changes the list. Works only on List. Example : mera_list = …
Educative
educative.io › answers › how-to-use-the-reverse-and-reversed-methods-in-python
How to use the reverse() and reversed() methods in Python
It modifies the list but the reversed() method gives an iterator to help traverse the given list in reversed order.
Plain English
python.plainenglish.io › understanding-reverse-vs-reversed-in-python-4ce1750722d4
Understanding reverse vs reversed in Python | by Allwin Raju | Python in Plain English
November 19, 2024 - The reverse() method is specific to mutable sequences, such as lists. It modifies the sequence in place, which means the original data structure is updated and no new object is created.
Medium
vinitatimesq29.medium.com › difference-between-reverse-and-reversed-built-in-functions-in-python-87761c2628e3
Difference between Reverse() and Reversed() built-in functions in Python. | by Vinita | Medium
August 20, 2020 - While both reverse() and reversed() are built-in functions and they are used to reverse a list but we need to understand two differences w.r.t.
YouTube
youtube.com › watch
Python's reverse() Vs reversed() | 2MinutesPy - YouTube
#reverse #reversed #list #coding #python #pythonprogramming #2minutespy 🖐Hey, want to know what are Python's reverse() and reversed() and how they differ...
Published January 15, 2024
Anujcodes
anujcodes.com › choosing-the-right-method-for-reversing-sequences-in-python-reverse-vs-reversed
Reverse a List in Python: reverse() vs. reversed() – Anuj Sharma
Python provides two common ways to reverse a list: reverse() method (modifies the list in-place) reversed() function (returns a reversed iterator) Each has its own advantages depending on the use case. Works only on lists. Modifies the original list directly (in-place).
Reddit
reddit.com › r/python › reversed vs [::-1]
r/Python on Reddit: reversed vs [::-1]
June 24, 2014 -
I always thought that slice operation for reversing of the list or something else is fastest one. But after watching "Transforming Code into Beautiful, Idiomatic Python" on youtube I have decided to compare slice and reversed method to each other. Obviously reversed is faster than slicing when we assign the result to new variable. But when we want just to reverse without having new variable results are roughly the same or even better for slicing . Here is the graph and tested code
graphs!
import timeit example = ''' d = [1,2,3,4,5,6,7,8,9,0] d = reversed(d) ''' example2 = ''' d = [1,2,3,4,5,6,7,8,9,0] d = d[::-1] ''' print(timeit.timeit(example, number=100000000)) print(timeit.timeit(example2, number=100000000)) import timeit example = ''' d = [1,2,3,4,5,6,7,8,9,0] new_var = reversed(d) ''' example2 = ''' d = [1,2,3,4,5,6,7,8,9,0] new_var = d[::-1] ''' print(timeit.timeit(example, number=100000000)) print(timeit.timeit(example2, number=100000000))
Should programmer choose carefully between slicing and reversed?
Top answer 1 of 3
9
Note that reversed() doesn't return a list, it returns an iterator. Your code snippets aren't equivalent. Should programmer choose carefully between slicing and reversed? Only if you have huge lists that take up gigabytes of memory. Just choose the one that expresses your intent more clearly.
2 of 3
9
Slicing creates a whole new list, copying every element from the original. reversed() just returns an iterator that walks the original list in reverse order, without copying anything. This benchmark isn't really going to show anything of interest because the lists are so small -- it's all statistical noise. The time it takes to copy 10 elements is going to be lost in the margins. Plus, you're including the time it takes to create the list in the benchmark, further muddying the results. Try it with lists of substance and you'll see a vast difference: >>> from random import random >>> foo = [random() for _ in range(1000000)] >>> timeit bar = foo[::-1] 100 loops, best of 3: 4.56 ms per loop >>> timeit bar = reversed(foo) 1000000 loops, best of 3: 209 ns per loop The latter is more than 20,000 times faster. And it should be, because it's not actually doing any work, whereas the slice is doing a ton of work. Bottom line, you should only use a slice if you actually need a new copy of the data, which is rare. You should use reversed() for everything else, such as iterating over the data in reverse order.
DEV Community
dev.to › sachingeek › what-is-the-difference-between-reverse-and-reversed-in-python-54ik
What is the Difference Between Reverse and Reversed in Python - DEV Community
September 9, 2023 - As we discussed earlier, the reverse() function from Python List is used to reverse the elements in a List.
Medium
geekpython.medium.com › reverse-vs-reversed-comparing-two-same-looking-functions-e1a02c8215a0
Reverse Vs Reversed — Comparing Two Same-Looking Functions | by Sachin Pal | Medium
November 30, 2022 - We cannot use the reverse function on the string data type or any other data type. The reverse() function can only be used for the list data type. Python reversed() function takes a sequence and returns the reversed iterator object.
Sarthaks eConnect
sarthaks.com › 3465841 › what-is-the-difference-between-reverse-and-reversed-methods-in-python
What is the difference between reverse() and reversed() methods in Python? - Sarthaks eConnect | Largest Online Education Community
What is the difference between reverse() and reversed() methods in Python?
GeeksforGeeks
geeksforgeeks.org › python › python-reversed-function
Python reversed() Method - GeeksforGeeks
February 17, 2026 - Explanation: reversed(a) returns an iterator, list() converts the iterator into a list and the elements appear in reverse order.
Plain English
python.plainenglish.io › 1-vs-reversed-which-one-is-the-smart-way-to-reverse-a-list-da6ee6c22e2d
[::-1] vs reversed() — Which One Is the Smart Way to Reverse a List? | by Leo Liu | Python in Plain English
April 24, 2025 - New Python content every day. Follow to join our 3.5M+ monthly readers. ... Reversing a list is one of the most common tasks in Python. But when it comes to choosing between [::-1] (slicing) and reversed() (built-in function), most Pythonistas have strong opinions.
Real Python
realpython.com › python-reverse-list
Reverse Python Lists: Beyond .reverse() and reversed() – Real Python
June 28, 2023 - To meet the first challenge, you can use either .reverse() or a loop that swaps items by index. For the second, you can use reversed() or a slicing operation. In the next sections, you’ll learn about different ways to accomplish both in your code. ... Like other mutable sequence types, Python lists implement .reverse().
Educative
educative.io › answers › how-to-use-reverse-in-python
How to use reverse() in Python
On the other hand, reverse() does not take any arguments, nor does it return anything.
Note.nkmk.me
note.nkmk.me › home › python
Reverse a List, String, Tuple in Python: reverse, reversed | note.nkmk.me
August 16, 2023 - In Python, you can reverse a list using the reverse() method, the built-in reversed() function, or slicing. To reverse a string (str) and a tuple, use reversed() or slicing. Reverse a list using the r ...
Exercism
exercism.org › tracks › python › exercises › reverse-string › approaches › built-in-reversed
Explore the 'Use the built-in reversed() function.' approach for Reverse String in Python on Exercism
This has over-complicated reversed(), as it can be called directly on the input string with almost no overhead. This has also incurs the performance hit of repeated concatenation to the 'output' string. While this approach looks as if it would be similar to the first, it is actually O(n**2) in time complexity due to string concatenation. It was also the slowest in benchmarks. As a (very) rough comparison, below is a timing table for these functions vs the canonical reverse slice: