windowed.py

class _NoPadding: pass

_Chunk_T = TypeVar("_Chunk_T")

def _windowed(iterable: Iterable[_Chunk_T], size: int, step: int = 1, padding: _NoPadding|Any = _NoPadding()) -> Iterable[Iterable[_Chunk_T|None]]:
    it = iter(iterable)
    chunk: List[_Chunk_T|Any] = []
    while True:
        # Pop step items from the buffer
        if chunk:
            for _ in range(step):
                chunk.pop(0)
        # Fill the buffer
        for _ in range(size - len(chunk)):
            try:
                chunk.append(next(it))
            except StopIteration:
                # We've hit the end, add padding
                if not isinstance(padding, _NoPadding):
                    if len(chunk) != size:
                        for _ in range(size - len(chunk)):
                            chunk.append(padding)
                yield chunk
                return
        # Yield the buffer
        yield chunk

for chunk in _windowed([1,2,3,4,5,6,7], 4, 2, padding=0):
    print(list(chunk))