Nearest neighbor in python

For example, I once needed code to do fast calculation of nearest-neighbors of a given data point

First google hit for "nearest neighbor" is scikit-learns k nearest neighbor classifier, which links to the BallTree and KDTree classes it uses for neighbor finding:

• https://scikit-learn.org/stable/modules/neighbors.html
• https://scikit-learn.org/stable/modules/generated/sklearn.neighbors.BallTree.html#sklearn.neighbors.BallTree
• https://scikit-learn.org/stable/modules/generated/sklearn.neighbors.KDTree.html#sklearn.neighbors.KDTree

Little more googling about those algorithms gives you:

• https://docs.scipy.org/doc/scipy/reference/generated/scipy.spatial.cKDTree.html

Also, researching nearest neighbors in generall, will give you the answer, that a KDTree is one of the most efficient algorithms to do this and googling
kdtree python will yield the scipy implementation as first hit.

Review the linked scikit-learn neighbors documentation and the BallTree, KDTree, and cKDTree references first. The issue names no repository file, test, implementation scope, or acceptance criteria, so clarify the intended Python change and its completion criteria before coding.