Grid-like movement in Python

Question

After importing a bunch of objects into a Maya scene, all at origin, I'd like to organize them in a grid-like arrangement with every cell of the grid filled. I came up with a solution, but it doesn't really work as more rows and columns get created.

It leaves empty spots like in this illustration:

Any idea on how to fix the arrangement?

The code I currently have:

import maya.cmds as mc

#for iteration loops
offsetAmtZ= 40
offsetAmtX= 40
switchBool= True
diagonalMove= True

#select all ctrls
mc.select(all=True)
allCtrls= mc.ls(sl=True)

for each in allCtrls:
    if diagonalMove== True:
        mc.move(offsetAmtX,0,offsetAmtZ, each)
        diagonalMove= False
    else:
        if switchBool== True:
            mc.move(0,0,offsetAmtZ, each)
            switchBool= False
            offsetAmtZ= offsetAmtZ + 40
        else:
            mc.move(offsetAmtX,0,0, each)
            switchBool= True
            offsetAmtX= offsetAmtX + 40
            diagonalMove= True