Easiest way to perform modular matrix inversion with Python?

Question

I\'d like to take the modular inverse of a matrix like [[1,2],[3,4]] mod 7 in Python. I\'ve looked at numpy (which does matrix inversion but not modular matrix inversion) an

Answer 1

'sympy' package Matrix class function 'sqMatrix.inv_mod(mod)' computes modulo matrix inverse for small and arbitrarily large modulus. By combining sympy with numpy, it becomes easy to compute modulo inverse of 2-D numpy arrays (see the code snippet below):

enter code here

import numpy
from sympy import Matrix

    def matInvMod (vmnp, mod):
    nr = vmnp.shape[0]
    nc = vmnp.shape[1]
    if (nr!= nc):
        print "Error: Non square matrix! exiting"
        exit()
    vmsym = Matrix(vmnp)
    vmsymInv = vmsym.inv_mod(mod)
    vmnpInv = numpy.array(vmsymInv)
    print "vmnpInv: ", vmnpInv, "\n"
    k = nr
   vmtest = [[1 for i in range(k)] for j in range(k)]  # just a 2-d list
   vmtestInv = vmsym*vmsymInv
   for i in range(k):
      for j in range(k):
         #print i, j, vmtrx2[i,j] % mod
         vmtest[i][j] = vmtestInv[i,j] % mod
   print "test vmk*vkinv % mod \n:", vmtest
   return vmnpInv

if __name__ == '__main__':
    #p = 271
    p = 

115792089210356248762697446949407573530086143415290314195533631308867097853951 vm = numpy.array([[1,1,1,1], [1, 2, 4, 8], [1, 4, 16, 64], [1, 5, 25, 125]])
#vminv = modMatInv(vm, p) vminv = matInvMod(vm, p) print vminv vmtestnp = vm.dot(vminv)%p # test mtrx inversion print vmtestnp