Gurobi Python "Either or" constraint

Question

I am creating an optimization model in Gurobi and want to add two constraints, of which only one has to be fulfilled. So either A or B, both together are impossible.

My idea was to add binary variables and create the following:

    if A:
       binary=1
    elif B:
       binary=1
    else:
       binary=0

And then I wanted to use

 m.addConstr(binary>=1)

but apparently that's an unsupported operand type for 'bool' and 'Nonetype'. Does anyone know to solve this problem?