python + operator overloading issue

Question

I am trying to implement addition function of Matrix. (that is, adding two matrixes) I am doing this by overloading addition function so that two matrix can be added. For this Matrix class, I inherited Grid class to implement.

I seem to have a problem in __add__ method here but can quite figure it out. The error says AttributeError: 'Matrix' Object has no attibute '_data'.

Here is my code. Please can anyone help? or explain?

thanks

from Grid import Grid

class Matrix(Grid):
    def __init__(self, m, n, value=None):
        self.matrix = Grid(m, n)
        self.row = m
        self.col = n
    def insert(self, row, col, value):
        self.matrix[row][col] = value
        print self.matrix
    def __add__(self, other):
        if self.row != other.row and self.column != other.column:
            print " Matrixs are not indentical."
        else:
            for row in xrange(self.row):
                for col in xrange(self.col):
                    self.matrix[row][col] = self.matrix[row][col] + other[row][col]
        return self.matrix

Here is the Grid class which I inherited.

from CArray import Array

class Grid(object):
    """Represents a two-dimensional array."""
    def __init__(self, rows, columns, fillValue = None):
        self._data = Array(rows)
        for row in xrange(rows):
            self._data[row] = Array(columns, fillValue)
    def getHeight(self):
        """Returns the number of rows."""
        return len(self._data)
    def getWidth(self):
        "Returns the number of columns."""
        return len(self._data[0])
    def __getitem__(self, index):
        """Supports two-dimensional indexing 
        with [row][column]."""
        return self._data[index]
    def __str__(self):
        """Returns a string representation of the grid."""
        result = ""
        for row in xrange(self.getHeight()):
            for col in xrange(self.getWidth()):
                result += str(self._data[row][col]) + " "
            result += "\n"
        return result

Rob Wouters · Accepted Answer · 2012-01-15 07:58:29Z

7

You didn't call inherited class constructor and, hence, _data is not defined in your class. Try adding the following in Matrix init:

super(Matrix, self).__init__(m, n, fillValue=value)

edited Jan 15, 2012 at 7:58

Rob Wouters

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answered Jan 15, 2012 at 6:26

real4x

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Comments

Rob Wouters · Accepted Answer · 2012-01-15 07:11:31Z

3

You have to call the parent's __init__ from your child __init__. Add this to Matrix.__init__:

super(Matrix, self).__init__(m, n, fillValue=value)

edited Jan 15, 2012 at 7:11

answered Jan 15, 2012 at 6:25

Rob Wouters

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4 Comments

user1047092 Over a year ago

I should add your code into Matrix init? Is this what you mean?

Rob Wouters Over a year ago

@user1047092, yes. What it does is call Grid.__init__.

user1047092 Over a year ago

Well. After I added the code and tried a = Matrix(2, 3). It says Type Error: __init__() takes at most 4 arguments . I have no idea what's wrong with it.

Rob Wouters Over a year ago

@user1047092, I made an error in my answer. self should not be passed to __init__. I've fixed my answer above.

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