[FIXED] Can I substitute IndexedBase with numpy array

Issue

Can I substitute a IndexedBase with a numpy array to get a new sympy expression? Something like:

import numpy as np
import sympy as sy

A = sy.IndexedBase('A', shape=(5))
k = sy.IndexedBase('k', shape=(5))
i = sy.symbols('i',cls=sy.Idx)

expr1 = sy.Sum(A[i]/sy.exp(sy.I * k[i]),(i,1,5))

kz = np.arange(1,5)

expr2 = expr1.subs(k[:],kz[:])

last line = error.

Thanks!

Solution

Yes, you can:

In [6]: expr2 = expr1.replace(k, kz)

In [7]: expr2
Out[7]: 
  5                              
 ___                             
 ╲                               
  ╲    -ⅈ⋅[1, 2, 3, 4, 5][i]     
  ╱   ℯ                     ⋅A[i]
 ╱                               
 ‾‾‾                             
i = 1 

Beware that the summation range is wrong, Python arrays have zero as offset.

Answered By - Francesco Bonazzi