A windowed iterator with a configurable window and step size in Python.

iter-window.py

class Window:

    def __init__(self, *args, window=2, step=1):
        self.iterator = iter(*args)
        self.window = window
        self.step = step
        self.buffer = ()

    def __iter__(self):
        return self

    def __next__(self):
        if not self.buffer:
            for _ in range(self.window):
                self.buffer += (next(self.iterator),)
        else:
            new_elements = ()
            for _ in range(self.step):
                new_elements += (next(self.iterator),)
            self.buffer = self.buffer[self.step:] + new_elements

        return self.buffer


# Examples
iterator = Window([1, 2, 3, 4, 5], window=2, step=1)
assert next(iterator) == (1, 2)
assert next(iterator) == (2, 3)
assert next(iterator) == (3, 4)
assert next(iterator) == (4, 5)

iterator = Window([1, 2, 3, 4, 5], window=3, step=1)
assert next(iterator) == (1, 2, 3)
assert next(iterator) == (2, 3, 4)
assert next(iterator) == (3, 4, 5)

iterator = Window([1, 2, 3, 4, 5], window=2, step=2)
assert next(iterator) == (1, 2)
assert next(iterator) == (3, 4)

iterator = Window([1, 2, 3, 4, 5], window=3, step=2)
assert next(iterator) == (1, 2, 3)
assert next(iterator) == (3, 4, 5)