Created an 2D array:
bigFloorLayout = []       
        bigFloorLayout=[[False for row in range(0,45] for col in range(0,70]


for y in range (offsetY, storageY + offsetY):
            for x in range (offsetX, storageX + offsetX):
                bigFloorLayout[x][y] = True

Offset is a negative number, and thus accessing bigFloorLayout[0][-1], which did not yield "Index out of Bounds" as it should.
This is in Blender 2.81, so I have no idea what version of python it is.