a sliding window generator in python

sliding_window.py

def sliding_window(iterable, size, overlap=0):
    """
        >>> list(sliding_window([1, 2, 3, 4], size=2))
        [(1, 2), (3, 4)]
        >>> list(sliding_window([1, 2, 3], size=2, overlap=1))
        [(1, 2), (2, 3)]
        >>> list(sliding_window([1, 2, 3, 4, 5], size=3, overlap=1))
        [(1, 2, 3), (3, 4, 5)]
        >>> list(sliding_window([1, 2, 3, 4], size=3, overlap=1))
        [(1, 2, 3), (3, 4)]
        >>> list(sliding_window([1, 2, 3, 4], size=10, overlap=8))
        [(1, 2, 3, 4)]
    """
    start = 0
    end = size
    step = size - overlap
    if step <= 0:
        ValueError("overlap must be smaller then size")
    length = len(iterable)
    while end < length:
        yield tuple(iterable[start:end])
        start += step
        end += step
    yield tuple(iterable[start:])