在每个网格单元中查找数组的索引？

I have a set of data. They are distributed in x-y positions but they have other characteristics like size. I like to grid my data in x-y plane and then obtain the grid index for each point and then compute the mean or standard deviation of size in each grid cell. I would like to see whether there is a correlation with the position in x-y plane with the size or not. The old fashion way is to write two loops and make a 3D matrix to keep the index of data in each cell. I am wondering whether there is a class in numpy or python which does this?I have a set of data. They are distributed in x