how to count number of points within a polygon

poly_contains.py

def count_kps_within_poly(polygon, keypoints):
    from matplotlib.collections import PolyCollection
    path = PolyCollection([polygon]).get_paths()[0]
    return np.sum(path.contains_points(keypoints))

assert 2 == count_kps_within_poly(
  [(0, 0), (100, 0), (200, 100), (100, 100), (0, 100)],
  [(50, 50), (200, 0), (1, 1)]
)