sumsympycalculus

Sympy summation with indexed variable

I try to create a sympy expression with a Sum with an indexed variable as previous explain here However, I can not do lambdify of this expression and give an array to get the sum calculated. Is this impossible?

Solution

  • Perhaps like this?

    from sympy.abc import i
s = Sum(Indexed('x',i),(i,1,3))
f = lambda x: Subs(s.doit(), [s.function.subs(s.variables[0], j)
for j in range(s.limits[0][1], s.limits[0][2] + 1)], x).doit()

>>> f((30,10,2))
42