import sympy as sym

x, a, b = sym.symbols('x, a, b')

# Creating an expression:

E1 = a*x + b

# Solving E1 = 0 for x:

E2 = sym.solve(E1, x)

# Defining function fun_f using lambdify():

fun_f = sym.lambdify([a, b], E2, 'numpy')

# Calculating values from the function by invoking
# fun_f with same named arguments as in lambdify:
# [0] addresses first element in the list val_fun_f:

val_fun_f = fun_f(a=2, b=3)[0]

print('val_fun_f =', val_fun_f)