please how to create a matrix in python??

[amine1978]

please I would like to write a fonction that takes as argument a matrix, 2 integers describing a cell coordinate and a value that set the corresponding cell to the value?????????
please help me

[bvdet]

please I would like to write a fonction that takes as argument a matrix, 2 integers describing a cell coordinate and a value that set the corresponding cell to the value?????????
please help me

Maybe this will help:

# A simple matrix
# This matrix is a list of lists
# Column and row numbers start with 1

class Matrix(object):
    def __init__(self, cols, rows):
        self.cols = cols
        self.rows = rows
        # initialize matrix and fill with zeroes
        self.matrix = []
        for i in range(rows):
            ea_row = []
            for j in range(cols):
                ea_row.append(0)
            self.matrix.append(ea_row)

    def setitem(self, col, row, v):
        self.matrix[col-1][row-1] = v

    def getitem(self, col, row):
        return self.matrix[col-1][row-1]

    def __repr__(self):
        outStr = ""
        for i in range(self.rows):
            outStr += 'Row %s = %s\n' % (i+1, self.matrix[i])
        return outStr


a = Matrix(4,4)
print a
a.setitem(3,4,'55.75')
print a
a.setitem(2,3,'19.1')
print a
print a.getitem(3,4)

Output:

>>> Row 1 = [0, 0, 0, 0]
Row 2 = [0, 0, 0, 0]
Row 3 = [0, 0, 0, 0]
Row 4 = [0, 0, 0, 0]

Row 1 = [0, 0, 0, 0]
Row 2 = [0, 0, 0, 0]
Row 3 = [0, 0, 0, '55.75']
Row 4 = [0, 0, 0, 0]

Row 1 = [0, 0, 0, 0]
Row 2 = [0, 0, '19.1', 0]
Row 3 = [0, 0, 0, '55.75']
Row 4 = [0, 0, 0, 0]

55.75
>>>

[bvdet]

Here's an iterator method for 'Matrix':

    def __iter__(self):
        for row in range(self.rows):
            for col in range(self.cols):
                yield (self.matrix, row, col)

Interactive:

>>> a = Matrix(3,3)
>>> x = 1.5
>>> for i,r,c in a:
... 	x = x*2
... 	i[r][c] = x
... 	
>>> a
Row 1 = [3.0, 6.0, 12.0]
Row 2 = [24.0, 48.0, 96.0]
Row 3 = [192.0, 384.0, 768.0]

>>>

[mohit ahuja]

Here's an iterator method for 'Matrix':

    def __iter__(self):
        for row in range(self.rows):
            for col in range(self.cols):
                yield (self.matrix, row, col)

Interactive:

>>> a = Matrix(3,3)
>>> x = 1.5
>>> for i,r,c in a:
... 	x = x*2
... 	i[r][c] = x
... 	
>>> a
Row 1 = [3.0, 6.0, 12.0]
Row 2 = [24.0, 48.0, 96.0]
Row 3 = [192.0, 384.0, 768.0]

>>>

I want to do something related to the columns of a matrix, I am using the same class as created, kindly help me with a function to get i-th column

[bvdet]

This should do the trick:

    def getcolumn(self, col):
        return [self.matrix[col-1][i] for i in range(self.rows)]

[Glenton]

Incidentally numpy has a matrix object that does the above and also supports matrix operations