i want to transform this result to type list, in python

Question

def sum(f,a,b):
  res = f[a]
  for n in range(a,b):
    res = res + f[n]
    n = n+1

  print(res)

N = 6 
k = np.linspace(-1*N/2,N/2,2*N+1)
x = np.linspace(0,N)
input =