Gurobi with python : how to construct conditional function in objective expression?

Question

I'm solving an integer programming problem using Gurobi in python, in which the objective expression includes some conditional functions.

Explicitly, the problem is modeled as follow:

max [sum(f(x_i, a_i)) + sum(g(x_i - x_[i-1]))]

f(x, a) = 0  if x = a; 
          1  otherwise.

g(x) = x  if x > 0;
       0  otherwise.

x_i in {1, 3, 5, 7, 10}
x_i are decision variables.
a_i, b_i are given parameters. a_i, b_i in {1, 3, 5, 7, 10}

How to construct the objective function in Gurobi with python?

Is there any other tools that can handle this problem?

Thank you for your helping!