Getting index of a certain element in a 2D numpy array

Question

I'm new to python so I need some help with this:

I have 2D array of numbers that represent density of a circle of material in a space and I want to locate the centre. So I want to get the index of the numbers representing the diameter and then the middle index will be the centre. In this code I only store the value of the density : tempdiameter.append(cell) I want the index of the cell itself. How can I do that. Also I don't want to use lists for diameter. so how can I create a dynamic 1D np array? Thanks

for row in x:
    for cell in row:
        if cell!=0:
            tempdensity+=cell
            tempdiameter.append(cell)

    if tempdensity>maxdensity:
            maxdensity=tempdensity
            if len(tempdiameter)>=len(diameter):
                   diameter=tempdiameter

    tempdensity=0
    tempdiameter=[]

Answer 1

To get the row with the highest number of non-zero cells and the highest sum you can do

 densities = x.sum(axis=1)
 lengths = (x > 0).sum(axis=1)
 center = x[(densities == densities.max()) & (lengths == lengths.max()]

Try to avoid using loops in numpy. Let me know if this isn't what you want and I'll try to answer it better. You should provide sample input/output when asking a question. You can also edit your question rather than adding comments.