SymPy - substitute sybolic entries in a matrix

Question

I have a python function which generates a sympy.Matrix with symbolic entries. It works effectively like:

import sympy as sp
M = sp.Matrix([[1,0,2],[0,1,2],[1,2,         


        

Answer 1

In the general case, I assume you're looking for an n-by-m matrix of symbolic elements.

import sympy

def make_symbolic(n, m):
    rows = []
    for i in xrange(n):
        col = []
        for j in xrange(m):
            col.append(sympy.Symbol('a%d%d' % (i,j)))
        rows.append(col)
    return sympy.Matrix(rows)

which could be used in the following way:

make_symbolic(3, 4)

to give:

Matrix([
[a00, a01, a02, a03],
[a10, a11, a12, a13],
[a20, a21, a22, a23]])

once you've got that matrix you can substitute in any values required.