Use the built-in reversed() function:
>>> a = ["foo", "bar", "baz"]
>>> for i in reversed(a):
... print(i)
...
baz
bar
foo
To also access the original index, use enumerate() on your list before passing it to reversed():
>>> for i, e in reversed(list(enumerate(a))):
... print(i, e)
...
2 baz
1 bar
0 foo
Since enumerate() returns a generator and generators can't be reversed, you need to convert it to a list first.
Top answer 1 of 16
1825
Use the built-in reversed() function:
>>> a = ["foo", "bar", "baz"]
>>> for i in reversed(a):
... print(i)
...
baz
bar
foo
To also access the original index, use enumerate() on your list before passing it to reversed():
>>> for i, e in reversed(list(enumerate(a))):
... print(i, e)
...
2 baz
1 bar
0 foo
Since enumerate() returns a generator and generators can't be reversed, you need to convert it to a list first.
2 of 16
268
You can do:
for item in my_list[::-1]:
print item
(Or whatever you want to do in the for loop.)
The [::-1] slice reverses the list in the for loop (but won't actually modify your list "permanently").
Reddit
reddit.com › r/learnpython › how can i loop through an array forward and then backwards and then forwards and... etc with the modulus operator?
r/learnpython on Reddit: How can I loop through an array forward and then backwards and then forwards and... etc with the modulus operator?
September 9, 2021 -
Say I have an array:
arr = [1,2,3,4,5]
and I want to output this using a simple counter and the modulus operator
1 2 3 4 5 4 3 2 1 2 3 4 5 ...
Is this possible? I know that you can loop through an array and start over at the beginning by doing
arr[count % len(arr)]
but how do I just switch directions instead of going back to the beginning?
Top answer 1 of 2
3
Given `n` is 1 less than the length of your array, you can increment and modulus some rotating index `i` against double `n` and then subtract `n`, take the absolute value and you get a bouncing number. It should be noted that you don't need to use any flags as suggested in other comments, but you do lose readability. Explanation: Take your example for an array of length 5, then `n=4`, `i` will rotate through values `[0, 1, 2, 3, 4, 5, 6, 7]` and subtracting `n` from each we get `[-4, -3, -2, -1, 0, 1, 2, 3]`, and the absolute values become `[4, 3, 2, 1, 0, 1, 2, 3]` which you can use to access the values at an index in your array. Try the following code: arr = [1, 2, 3, 4, 5] n = len(arr) - 1 i = n while True: curr_index = abs(i - n) print(arr[curr_index]) i = (i + 1) % (2 * n) and you will get output that looks like: 1 2 3 4 5 4 3 2 1 2 3 4 ...
2 of 2
2
I would just make a variable that specifies whether I'm going up or down and flip it when I hit 0 or len(arr)-1. Something like: arr = [1,2,3,4,5] i = 0 while True: print(arr[i]) if i==len(arr)-1: going_up = False elif i==0: going_up = True if going_up: i+=1 else: i-=1 I'm sure there's a far more elegant way to go about it (step 1 would be replacing the "if i==len(arr)-1" and "elif i==0" conditions with something involving modulo), but this does do the thing.
Can a for loop iterate over a list backwards?
Question Is it possible to have a for loop iterate over a list in reverse order without changing the list? Answer Yes, you can iterate over a list in reverse order without changing the list using the reversed() function. In this code, the list is printed in backward order but after the for ... More on discuss.codecademy.com
0
13
August 3, 2018Why isn't my loop iterating backwards in python?
Hint: Look up documentation on the ‘range’ function…does it actually do what you think it does given the two arguments you provided? Maybe you’re missing an argument? https://docs.python.org/3/library/stdtypes.html#range More on reddit.com
13
0
March 8, 2023How can I iterate over a list backward?
Question In the context of this code challenge, how can I iterate over a list backward? Answer There are a few ways that you can iterate over a list backward. One way is by utilizing the range() method, with a negative step value, so that the index decreases by 1 per element, essentially going ... More on discuss.codecademy.com
0
16
November 3, 2018Python iterate through a multidimensional numpy array in different ways - Stack Overflow
Now I want to iterate through this Array. First I want the output be a list or numpy array like this. More on stackoverflow.com
Videos
02:57
Using reversed to loop in reverse in Python - YouTube
03:00
02.1 Reverse looping array in python - Python List Exercises Tutorial ...
04:52
How to reverse a list/array with and without using built in method ...
17:42
"Reverse a List in Python" Tutorial: Three Methods & How-to Demos ...
03:05
Python Programming 24 - Reverse Iterator - YouTube
GeeksforGeeks
geeksforgeeks.org › python › backward-iteration-in-python
Backward iteration in Python - GeeksforGeeks
July 11, 2025 - s = "Python" # - len(s) - 1: Start at the last index # - -1: Ensures the loop stops after the first character # - -1: The step value to iterate backwards for i in range(len(s) - 1, -1, -1): print(s[i]) ... We can use slicing slicing notation [::-1] to reverse the order of elements in an iterable. This works for lists, tuples, and strings, but not for sets or dictionaries (since they are unordered). ... a = [1, 2, 3, 4, 5] #Loop through the List # reverse order using slicing(::-1) for item in a[::-1]: print(item) # same logic written using List comprehension # [print(item) for item in a[::-1]]
Real Python
realpython.com › python-reverse-list
Reverse Python Lists: Beyond .reverse() and reversed() – Real Python
June 28, 2023 - This loop iterates through a range object that goes from 0 to len(digits) // 2. Each iteration swaps an item from the first half of the list with its mirror counterpart in the second half.
Stack Abuse
stackabuse.com › bytes › traversing-a-list-in-reverse-order-in-python
Traversing a List in Reverse Order in Python
August 30, 2023 - The reversed() function is the most Pythonic way to reverse a list. It's simple, readable, and efficient. It's especially useful when you need to iterate over the list in reverse order, but don't want to modify the original list.
Steemit
steemit.com › python › @makerhacks › reversing-iteration-going-through-a-list-forwards-and-backwards-in-python
Reversing Iteration: Going through a list forwards and backwards in Python — Steemit
May 29, 2018 - One of the things Python lacks is the in-built ability to go back one item when iterating through a list. Yes, you can reverse the whole list, or work from the end, but if you are in the middle of the list you can not just skip back one item. There is no undo. Fortunately, you CAN iterate via the index number of the array...
Medium
medium.com › becoming-a-better-software-developer › undetstanding-python-iterators-reversed-iteration-35f1c1d16196
Undetstanding Python Iterators: Reversed Iteration | by Saleem Latif | Becoming a better Software Developer | Medium
March 8, 2023 - Reversed iteration is a technique that allows you to iterate over a sequence of elements in reverse order. In Python, you can reverse iterate over a sequence by using the reversed() function.
Spark By {Examples}
sparkbyexamples.com › home › python › python for loop in backwards
Python For Loop in Backwards - Spark By {Examples}
May 31, 2024 - Usually loop iterations start from front side if you want to get the loop iterations from back side rather than the front side you can use reversed() function. Pass range() function into reversed() function will reverse the range() function ...
TutorialsPoint
tutorialspoint.com › backward-iteration-in-python
Backward iteration in Python
August 7, 2019 - This method involves slicing the list which starts from the position -1 and go backwards till the first position. We use a for loop with an iterator used as the index of the element in the list.
Quora
quora.com › Python-How-do-I-iterate-over-a-sequence-in-reverse-order
Python: How do I iterate over a sequence in reverse order? - Quora
Answer (1 of 4): What sort of sequence ? If the sequence is slicable (ie a list, or a tuple or s string or something that behaves like One of the above) then you can reverse slice : [code]for elem in sequence[::-1]: print(elem) [/code]If the sequence isn’t slicable (for instance it is a gene...
Codecademy
codecademy.com › article › how-to-reverse-a-list-in-python
How to Reverse a List in Python | Codecademy
This example demonstrates using reversed() to reverse a mixed data type list and iterate through reversed elements without creating a new list:
Python Morsels
pythonmorsels.com › looping-in-reverse
Looping in reverse - Python Morsels
May 27, 2025 - If you're working with a list, a string, or any other sequence in Python, you can reverse that sequence using Python's slicing syntax: >>> colors = ["purple", "blue", "green", "pink", "red"] >>> colors[::-1] ['red', 'pink', 'green', 'blue', 'purple'] The syntax looks weird, but it does work. If we wanted to write a for loop that iterated over our list from the end to the beginning, we could loop over the reversed slice of that list:
Codecademy Forums
discuss.codecademy.com › frequently asked questions › python faq
Can a for loop iterate over a list backwards? - Python FAQ - Codecademy Forums
August 3, 2018 - Question Is it possible to have a for loop iterate over a list in reverse order without changing the list? Answer Yes, you can iterate over a list in reverse order without changing the list using the reversed() function.
Reddit
reddit.com › r/learnprogramming › why isn't my loop iterating backwards in python?
r/learnprogramming on Reddit: Why isn't my loop iterating backwards in python?
March 8, 2023 -
Basically, I wanted the loop to start from the last index and work that way done. However, I am not getting anything.
listr = [10,20,30,50]
count = 0
for i in range(len(listr),-1):
count +=1
print(listr[i], count)
print('-----') Top answer 1 of 4
10
Hint: Look up documentation on the ‘range’ function…does it actually do what you think it does given the two arguments you provided? Maybe you’re missing an argument? https://docs.python.org/3/library/stdtypes.html#range
2 of 4
5
range(start, stop, step) if you just give two arguments, the function will interprete it as start and stop.
Spark By {Examples}
sparkbyexamples.com › home › python › reverse an array in python
Reverse an Array in Python - Spark By {Examples}
May 31, 2024 - To iterate range(len(arr)-1, -1, -1) use for loop, it will return an array of elements in the reversing order. Related: In Python, you can use for loop to iterate iterable objects in reversing order and get them in backwards directions.
Codecademy Forums
discuss.codecademy.com › frequently asked questions › python faq
How can I iterate over a list backward? - Python FAQ - Codecademy Forums
November 3, 2018 - Answer There are a few ways that you can iterate over a list backward. One way is by utilizing the range() method, with a negative step value, so that the index decreases by 1 per element, essentially going backward in the list.
Towards Data Science
towardsdatascience.com › home › latest › how to reverse python lists more efficiently
How To Reverse Python Lists More Efficiently | Towards Data Science
January 20, 2025 - Return a reverse [iterator](https://docs.python.org/3/glossary.html#term-iterator). seq must be an object which has a __reversed__() method or supports the sequence protocol (the __len__() method and the __getitem__() method with integer arguments starting at 0). This approach is recommended when it comes to performing backwards iteration over a list.
W3Schools
w3schools.com › python › ref_list_reverse.asp
Python List reverse() Method
Python Examples Python Compiler ... Q&A Python Bootcamp Python Certificate Python Training ... The reverse() method reverses the sorting order of the elements. ... The built-in function reversed() returns a reversed iterator ...
Reddit
reddit.com › r/learnpython › iterate over a string in reverse
r/learnpython on Reddit: iterate over a string in reverse
February 7, 2023 -
I want to iterate over a string in reverse. I googled it and found this way
for i in range(len(k)-1, 0-1, -1):
but to be honest I don't understand it. can you please explain it to me?
also, I would love it if you guys can suggest other methods
Top answer 1 of 3
6
https://docs.python.org/3/library/functions.html#reversed
2 of 3
2
This is not the approach you should take. reversed linked to by u/PaulRudin is a better tool here. But to explain the code; range takes up to 3 arguments. The first is the starting point. The second is the end point (this value will terminate the iteration and not be yielded back. The third is the step size. This is the amount by which the initial value will be modified by, until it reaches the end value. So if I pass in range(1, 5, 1) I will get back the values: 1, 2, 3, 4 If I was use to range(0, 10, 2) I get: 0, 2, 4, 6, 8 However, using range(10, 0, -2) gives 10, 8, 6, 4, 2 In this code you are starting from the end of some string (the length less one to get the last index) and taking steps backwards by 1 each iteration. The end point is -1 to include the 0 index (written strangely here, but this is a slightly strange construct anyway).