Reverse a List in Python Without Using reverse() Function

While reverse() is the easiest and most direct method to reverse a list in Python it's useful to know alternative approaches to reverse a list without relying on this function.

Using Slicing

We can use Python’s list-slicing feature to create a reversed list version without modifying the original one.

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

# Reversing using slicing
a_reversed = a[::-1]
print(a_reversed)

[5, 4, 3, 2, 1]

• a[::-1] creates a new list with the elements of a in reverse order. The -1 in the slice means we step through the list backwards.

Let's look into the other alternatives methods:

Using for Loop

Another way to reverse a list is by using a simple loop. We can iterate over the list and append the elements in reverse order to a new list.

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

# New list to hold reversed values
b = []

# Loop through the original list in reverse
for i in range(len(a) - 1, -1, -1):
    b.append(a[i])

print(b)

[5, 4, 3, 2, 1]

Using List Comprehension

List comprehension is a more compact way to reverse a list by iterating over the original list in reverse order and constructing a new list.

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

# Using list comprehension to reverse the list
reversed_list = [a[i] for i in range(len(a) - 1, -1, -1)]
print(reversed_list)  

[5, 4, 3, 2, 1]