ot sort them if False. If
    None, does not sort single point queries, but does sort
    multi-point queries which was the behavior before this option
    was added.

    .. versionadded:: 1.6.0
return_length : bool, optional
    Return the number of points inside the radius instead of a list
    of the indices.

    .. versionadded:: 1.6.0

Returns
-------
results : list or array of lists
    If `x` is a single point, returns a list of the indices of the
    neighbors of `x`. If `x` is an array of points, returns an object
    array of shape tuple containing lists of neighbors.

Notes
-----
If you have many points whose neighbors you want to find, you may save
substantial amounts of time by putting them in a KDTree and using
query_ball_tree.

Examples
--------
>>> import numpy as np
>>> from scipy import spatial
>>> x, y = np.mgrid[0:5, 0:5]
>>> points = np.c_[x.ravel(), y.ravel()]
>>> tree = spatial.KDTree(points)
>>> sorted(tree.query_ball_point([2, 0], 1))
[5, 10, 11, 15]

Query multiple points and plot the results:

>>> import matplotlib.pyplot as plt
>>> points = np.asarray(points)
>>> plt.plot(points[:,0], points[:,1], '.')
>>> for results in tree.query_ball_point(([2, 0], [3, 3]), 1):
...     nearby_points = points[results]
...     plt.plot(nearby_points[:,0], nearby_points[:,1], 'o')
>>> plt.margins(0.1, 0.1)
>>> plt.show()

r 