I am trying to make a class a record within a numpy array. The piece of code I am working on has the following class within it: class Record: def __init__(self): self.count = 0 self.level = 0 self.list = [] self.max = None self.min = None def add(self, value): self.count += 1 self.level += value if self.max is None: self.max = value else: self.max = max(value, self.max) if self.min is None: self.min = value else: self.min = min(value, self.min) self.list.append(value) when I use this class manually it works as I would expect and does what I want eg: x = Record() x.add(42) x.add(22) x.add(342) x.add(44) x.add(12) x.add(2) for eachitem in x.list: print eachitem 42 22 342 44 12 2 It's Okay to here. When I create the following code: vegetation_matrix = numpy.empty(shape=(x_bins+1,y_bins+1)) for each_line in point_scandata: matrix_x = round_to_value((each_line[0]-x_offset),horizontal_precision) matrix_y = round_to_value((each_line[1]-y_offset),horizontal_precision) vegetation_matrix[matrix_x][matrix_y] = Record() I get an error: Traceback (most recent call last): File "MatrixTo3bynArray.py", line 159, in <module> vegetation_matrix[matrix_x][matrix_y] = Record() SystemError: error return without exception set I would ask the universal what am I doing wrong, but how about I ask in this particular situation, what am I doing wrong? Can anybody guide me through this problem? Regards, David