Python - K element reverse slicing

Reverse slicing is defined by creating a slice starting at the length of the string and ending at the 0th index. To reverse the list elements, it will use negative value notation and we can get the reverse order of the original list elements. In Python, we have some inbuilt functions like append(), len() and range() which will be used to solve K-element reverse slices.

grammar

The following syntax is used in the example -

append()

This built-in method in Python can be used to add elements to the end of a list.

len()

The built-in function len() is used to return the length of the object.

range()

range() is a built-in function in Python that returns a sequence of numbers based on a given range.

reversed()

reverse() is a built-in function in Python that returns the given list elements in reverse order.

Use slices

In the following example, we will start the program with a function called rev_slice, which accepts parameters r_list and k to receive input values. Next, using slice notation, reverse the elements based on the K value and get the desired result.

Example

def rev_slice(r_list, k):
    return r_list[-k:][::-1]
test_list = [2, 4, 20, 40, 60, 80]
k = 2
output = rev_slice(test_list, k)
print("The reverse slice based on the K element:\n", output)

Output

 The reverse slice based on the K element: [80, 60]

Use reverse()

In the example below we will use a recursive function that calls itself when needed. Next, use the built-in function reverse() that accepts the parameter -t_list[-k:] to reverse all elements of the list form.

Example

def rev_slice(t_list, k):
    return list(reversed(t_list[-k:]))
test_list = [1, 2, 3, 4, 5]
# Initialize the K value
k = 2
# Calling function
output = rev_slice(test_list, k)
print("The following K element reverse:", output)

Output

 The following K element reverse: [5, 4]

Use list comprehension

In the following example, the program uses a list comprehension that uses a for loop where the variable i iterates over the input list and uses the built-in function range() to simplify the sequence of indexes from start to end. To reverse K elements, it uses slice notation [::-1].

Example

def rev_slice(t_list, k):
    return [t_list[i] for i in range(len(t_list) - k, len(t_list))][::-1]
test_list = [2, 4, 20, 40, 11, 12]
k = 4
res = rev_slice(test_list, k)
print("The K reverse element are-",res)

Output

 The K reverse element are- [12, 11, 40, 20]

Use range() and append()

In the following example, we will start the program using the recursive function rev_slice(), which accepts two parameters - t_list and k, which will receive the input list elements and k value to process reverse slicing. Next, use the empty list in the variable reversed_slice to store the final result. Then use a for loop where the variable i iterates over the input list with the help of some built-in functions such as range() and len(). Keep going back to reversed_slice to get specific list elements.

Example

def rev_slice(t_list, k):
    reversed_slice = []
    for i in range(len(t_list) - 1, len(t_list) - k - 1, -1):
        reversed_slice.append(t_list[i])
    return reversed_slice
test_list = [10, 20, 30, 40, 50, 60, 70, 80]
k = 3
res = rev_slice(test_list, k)
print("Following K reverse element:", res)

Output

 Following K reverse element: [80, 70, 60]

in conclusion

We explored K-element reverse slicing in Python, which provides a simple way to obtain a subset of a list. It is used to process large data sets, extracting precise parts of the list in reverse order. This type of code solves specific tasks that require analyzing data in reverse fashion.

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