Set not initializing in Pyomo

Question

I'm trying to define a set of variables in Pyomo the following way:

def initA ( i , model ):
   for i in range(p)
      yield -1

def initB ( i , model ):
   for i in range(p)
      yield random.randrage(-999999, 999999)

# variables
model.A = Set()
model.B = Set()
model.a = Var(model.A, within=IntegerSet, bounds=(-1,1), initialize=initA)
model.b = Var(model.B, domain=Reals, initialize=initB)

I use Pyomo's printing function to verify the sets and i get this:

a : Size=0, Index=A
  Key : Lower : Value : Upper : Fixed : Stale : Domain
b : Size=0, Index=B
  Key : Lower : Value : Upper : Fixed : Stale : Domain

And when I try to solve the model I receive this error:

ERROR: Rule failed when generating expression for objective OBJ: KeyError:
"Index '1' is not valid for indexed component 'a'"

Is there something I'm missing when creating the variable sets?

Answer 1

You don't need the internal for loops in the initialization functions. Also, the model needs to be the first argument in these functions:

def initA(model, i):
   return -1

def initB(model, i):
   return random.randrage(-999999, 999999)

# variables
model.A = Set()
model.B = Set()
model.a = Var(model.A, within=IntegerSet, bounds=(-1,1), initialize=initA)
model.b = Var(model.B, domain=Reals, initialize=initB)