Iterate over a List or String in Reverse order in Python

# Table of Contents

1. Iterate over a List in reverse order with Index
2. Iterate over a List in reverse order
3. Iterate over a List in reverse order using a negative step
4. Iterate over a String backward in Python
5. Iterate over a string backward using a negative step
6. Iterate over a string backward with index

# Iterate over a List in reverse order with Index

To iterate over a list in reverse order with index:

1. Use the enumerate() function to get access to the index.
2. Convert the enumerate object to a list and reverse the list.
3. Use a for loop to iterate over the list in reverse order.

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my_list = ['a', 'b', 'c', 'd']


for index, item in reversed(list(enumerate(my_list))):
    print(index, item)  # 👉️ 3 d 2 c 1 b 0 a

We used the enumerate function to get access to the index when iterating.

The enumerate() function takes an iterable and returns an enumerate object containing tuples where the first element is the index and the second is the item.

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my_list = ['apple', 'banana', 'melon']

for index, item in enumerate(my_list):
    print(index, item)  # 👉️ 0 apple, 1 banana, 2 melon

We used the list() class to convert the enumerate object to a list because the first argument the reversed() function takes is a sequence.

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my_list = ['a', 'b', 'c', 'd']

# 👇️ [(0, 'a'), (1, 'b'), (2, 'c'), (3, 'd')]
print(list(enumerate(my_list)))

# 👇️ [(3, 'd'), (2, 'c'), (1, 'b'), (0, 'a')]
print(list(reversed(list(enumerate(my_list)))))

The last step is to use a for loop to iterate over the list of tuples.

The first element in each tuple is the index and the second is the corresponding value.

# Iterate over a List in reverse order in Python

Use the reversed() function to iterate over a list in reverse order.

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my_list = ['a', 'b', 'c', 'd']

for item in reversed(my_list):
    print(item)  # 👉️ d c b a

The first example uses the reversed() function to reverse a list.

The reversed() function takes an iterator, reverses it and returns the result.

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my_list = ['a', 'b', 'c', 'd']

reversed_list = list(reversed(my_list))
print(reversed_list)  # 👉️ ['d', 'c', 'b', 'a']

However, if you only need to iterate over the list in reverse order, you can can do it directly.

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my_list = ['a', 'b', 'c', 'd']

for item in reversed(my_list):
    print(item)  # 👉️ d c b a

# Iterate over a List in reverse order using a negative step

Alternatively, you can use a negative step.

The slice with a step of -1 is used to reverse the list before iterating over it with a for loop.

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my_list = ['a', 'b', 'c', 'd']


for item in my_list[::-1]:
    print(item)  # 👉️ d c b a

We used a negative step to reverse the list before iterating over it.

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my_list = ['a', 'b', 'c', 'd']

# 👇️ ['d', 'c', 'b', 'a']
print(my_list[::-1])

The syntax for list slicing is my_list[start:stop:step].

# Iterate over a string backward in Python

You can also use the reversed() function to iterate over a string in reverse order.

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my_str = 'abcd'

# ✅ Iterate over a string in reverse order (reversed())

for char in reversed(my_str):
    print(char)  # 👉️ d, c, b, a

The first example uses the reversed() function to reverse a string.

The reversed() function takes an iterator, reverses it and returns the result.

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my_str = 'abcd'

for char in reversed(my_str):
    print(char)  # 👉️ d, c, b, a

# Iterate over a string backward using a negative step

Alternatively, you can use a negative step.

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my_str = 'abcd'


for char in my_str[::-1]:
    print(char)  # 👉️ d, c, b, a

We used a negative step to reverse the string before iterating over it.

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my_str = 'abcd'

reversed_str = my_str[::-1]
print(reversed_str)  # 👉️ dcba

The syntax for string slicing is my_string[start:stop:step].

# Iterate over a string backward with index

To iterate over a string backward with index:

1. Use the enumerate() function to get access to the index.
2. Convert the enumerate object to a list and reverse the list.
3. Use a for loop to iterate over the string in reverse order.

Copied!
my_str = 'abcd'


for index, char in reversed(list(enumerate(my_str))):
    print(index, char)  # 👉️ 3 d, 2 c, 1 b, 0 a

We used the enumerate function to get access to the index when iterating.

The enumerate() function takes an iterable and returns an enumerate object containing tuples where the first element is the index and the second is the item.

Copied!
my_str = 'abcd'

for index, char in enumerate(my_str):
    print(index, char)  # 👉️ 0 a, 1 b, 2 c, 3 d

We used the list() class to convert the enumerate object to a list because the first argument the reversed() function takes is a sequence.

Copied!
my_str = 'abcd'

# 👇️ [(0, 'a'), (1, 'b'), (2, 'c'), (3, 'd')]
print(list(enumerate(my_str)))

# 👇️ [(3, 'd'), (2, 'c'), (1, 'b'), (0, 'a')]
print(list(reversed(list(enumerate(my_str)))))

The last step is to use a for loop to iterate over the list of tuples.

The first element in each tuple is the index and the second is the corresponding character.

# Additional Resources

You can learn more about the related topics by checking out the following tutorials:

• Split a String, Reverse it and Join it back in Python
• Why does list.reverse() return None in Python