matrix_exp.py

import numpy as np, itertools, functools, operator

def matrix_exp(A, num_iters=100):
  inv_facs = itertools.accumulate(range(1,num_iters+1), operator.mul, initial=1)
  As = itertools.accumulate(range(num_iters), lambda Ap, _: np.dot(Ap, A), initial=A)
  return sum(1. / inv_fac * A for inv_fac, A in zip(inv_facs, As))