Basic numeric list
Input
sliding_windows([1, 2, 3, 4], 2)
Output
[[1, 2], [2, 3], [3, 4]]
All contiguous windows of size 2 with default step 1.
Full lesson preview
Generate sliding windows of size n
Create contiguous sliding windows from any sequence with a configurable step.
Python practice15 minList & Dictionary PatternsIntermediateLast updated March 20, 2026
Problem statement
Given a sequence (list, tuple, or string), produce all contiguous windows of length n. The windows should be taken by advancing the start index by 'step' each time. If n is greater than the sequence length, return an empty list. The function should work with any sliceable sequence and return windows of the same type elements (i.e., for strings return substrings, for lists return lists). Do not modify the original sequence.
Task
Implement a function that returns a list of contiguous windows (sublists or substrings) of size n from a sequence, supporting a step parameter.
Examples
Step greater than 1
Input
sliding_windows([1,2,3,4,5], 3, 2)
Output
[[1, 2, 3], [3, 4, 5]]
Windows start at indices 0 and 2 because step=2.
String input
Input
sliding_windows('abcdef', 3)
Output
['abc', 'bcd', 'cde', 'def']
Works on strings and returns substrings.
Input format
A sequence (list/tuple/string), integer n (window size), optional integer step (default 1).
Output format
A list of windows. Each window is of the same element type as the input (sublist for lists, substring for strings).
Constraints
n and step should be positive integers. If n > len(seq) return an empty list. The function must not mutate the input sequence.
Samples
Sample 1
Input
sliding_windows([1,2,3], 3)
Output
[[1, 2, 3]]
Window size equal to sequence length returns single window.