Traverse a list in reverse order in Python

This post will discuss how to traverse a list in reverse order in Python without modifying the original list.

1. Using built-in `reversed()` function

You can pass the list to the built-in function reversed(), which returns a reverse iterator and doesn’t modify the list.

if __name__ == '__main__':

a = [1, 2, 3, 4, 5]

for x in reversed(a):

print(x)

'''

Output:

'''

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If you need the indices, use the enumerate() function for getting the position index and corresponding value.

if __name__ == '__main__':

a = [1, 2, 3, 4, 5]

for i, v in reversed(list(enumerate(a))):

print(i, v)

'''

Output:

4 5

3 4

2 3

1 2

0 1

'''

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Another way to iterate with indices can be done in the following manner:

if __name__ == '__main__':

a = [1, 2, 3, 4, 5]

for i in range(len(a) - 1, -1, -1):

print(i, a[i])

'''

Output:

4 5

3 4

2 3

1 2

0 1

'''

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2. Using extended slicing

The [::-1] slice makes a copy of the list in reverse order, which can be used in the for-loop to print items in reverse order.

if __name__ == '__main__':

a = [1, 2, 3, 4, 5]

for x in a[::-1]:

print(x)

'''

Output:

'''

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That’s all about traversing a list in reverse order in Python.

Traverse a list in reverse order in Python

1. Using built-in reversed() function

2. Using extended slicing

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1. Using built-in `reversed()` function