Python Program to split string into k sized overlapping strings

Given a string, the task is to write a Python program to extract overlapping consecutive string slices from the original string according to size K. 

Example:

Input : test_str = ‘Geeksforgeeks’, K = 4

Output : [‘Geek’, ‘eeks’, ‘eksf’, ‘ksfo’, ‘sfor’, ‘forg’, ‘orge’, ‘rgee’, ‘geek’, ‘eeks’]

Explanation : Consecutive overlapping 4 sized strings are output.

Input : test_str = ‘Geeksforgeeks’, K = 6

Output : [‘Geeksf’, ‘eeksfo’, ‘eksfor’, ‘ksforg’, ‘sforge’, ‘forgee’, ‘orgeek’, ‘rgeeks’]

Explanation : Consecutive overlapping 6 sized strings are output.

Method 1: Using islice() + generator function + join()

In this, windows of size K are extracted using the islice(), and results are yielded in an intermediate way using yield. The final results are joined using join(). 

Python3

# Python3 code to demonstrate working of
# Overlapping consecutive K splits
# Using islice() + generator function + join()
from itertools import islice

# generator function
def over_slice(test_str, K):
    itr = iter(test_str)
    res = tuple(islice(itr, K))
    if len(res) == K:
        yield res
    for ele in itr:
        res = res[1:] + (ele,)
        yield res

# initializing string
test_str = 'Geeksforgeeks'

# printing original string
print("The original string is : " + str(test_str))

# initializing K
K = 4

# calling generator function
res = ["".join(ele) for ele in over_slice(test_str, K)]

# printing result
print("Overlapping windows : " + str(res))

Output:

The original string is : Geeksforgeeks

Overlapping windows : [‘Geek’, ‘eeks’, ‘eksf’, ‘ksfo’, ‘sfor’, ‘forg’, ‘orge’, ‘rgee’, ‘geek’, ‘eeks’]

Method 2: Using list comprehension + slicing

In this example, intermediate slices are performed using a slicing operation in a more pythonic way. Each window is extracted using slice notation.

Python3

# Python3 code to demonstrate working of
# Overlapping consecutive K splits
# Using list comprehension + slicing

# initializing string
test_str = 'Geeksforgeeks'

# printing original string
print("The original string is : " + str(test_str))

# initializing K
K = 4

# extracting window using slicing
res = [test_str[idx:idx + K] for idx in range(len(test_str) - K + 1)]

# printing result
print("Overlapping windows : " + str(res))

Output:

The original string is : Geeksforgeeks

Overlapping windows : [‘Geek’, ‘eeks’, ‘eksf’, ‘ksfo’, ‘sfor’, ‘forg’, ‘orge’, ‘rgee’, ‘geek’, ‘eeks’] 

The Time and Space Complexity of all the methods is :

Time Complexity: O(n)

Space Complexity: O(n)