如何修复 Pyomo 中的属性错误 model python

Question

I am trying to write a pyomo model in python3, but I am facing this error that I can't seem to figure out - 'list' object has no attribute 'is_expression_type'. Below is my pyomo model, any help would be appreciated.

    R_avg_tolist = [[0.00043159478649482775,
  0.00045388639592182584,
  0.0006735271301199177,
  0.00044026758948786,
  0.0037176592984565836]]

    Cov_list = [[5.884677519869241e-05,
  5.756542207262417e-05,
  6.017027849080026e-05,
  6.180151597797322e-05,
  -0.0005074353586106837],
 [5.756542207262417e-05,
  6.0380562653096757e-05,
  6.613608499966434e-05,
  6.737370769879904e-05,
  -0.0005362752804115953],
 [6.017027849080026e-05,
  6.613608499966434e-05,
  8.206495000024503e-05,
  8.01694525889321e-05,
  -0.0005958716888916681],
 [6.180151597797322e-05,
  6.737370769879904e-05,
  8.01694525889321e-05,
  0.00010129901491226823,
  -0.000608829853150321],
 [-0.0005074353586106837,
  -0.0005362752804115953,
  -0.0005958716888916681,
  -0.000608829853150321,
  0.007373689071617548]]

    import pyomo.environ as pyo
    
    # Optimization Problem
    def create_model(rho,R_avg,Cov):
        
        m = pyo.ConcreteModel()
        init_x = {}
        m.idx = pyo.Set(initialize=[0,1,2,3,4])
        for i in m.idx:
            init_x[i] = 0
        m.x = pyo.Var(m.idx,initialize=init_x,bounds=(0,None))
        
        def Obj_func(m):
            b = []
            mult_result = 0
            for i in m.idx:
                a = 0
                for j in m.idx:
                    a+= m.x[j]*Cov[j][i]
                b.append(a)
            for i in m.idx:
                mult_result += b[i]*m.x[i]
            
            return mult_result
        m.OBJ = pyo.Objective(rule=Obj_func)
        
        def constraint1(m):
            sum=0
            for i in m.idx:
              sum+=m.x[i]
              return sum ==100  
    
        m.C1 = pyo.Constraint(rule=constraint1(m))
        
        def constraint2(m):
            
            sum=0
            for i in m.idx:
              sum += R_avg_tolist[i]*m.x[i]
    
            return sum >=0.08
    
        m.C2 = pyo.Constraint(rule=constraint2(m))
        
        return m

When I run model using below code, I face the attribute error - 'list' object has no attribute 'is_expression_type'.

rho = 0.0008
model1 = create_model(rho,R_avg_tolist,Cov_list)

solver = SolverFactory('ipopt')
results = solver.solve(model1, tee = True)

Answer 1

Probably not what you want to hear, but your model has many syntax probs. It's obviously a course assignment... Do you have somebody (instructor/TA) to go over this with who can advise a bit?

You didn't include enough info about which line of code caused the issue, but there are several problem areas. I've posted many simple pyomo examples if you scan through some of them, you'll get some ideas, along with the documentation and whatever you have from your course notes....

A few pointers may help:

Do NOT overwrite keywords/functions by using them as variables. When you write:

sum = 0
sum ....

you are nuking the python function sum by making that name a variable and assigning it the value of 0. You should be using sum in several of your functions with verbiage like:

sum(m.X[i] for i in m.idx)    # or similar

You seem to be confused on making valid pyomo expressions. That is the core job of pyomo... to make expressions and fill the model. For example, in your constraint1 , you can just make an expression (without a function) and add it to your model. You can do a 1-liner there because the constraint is not a "for each". You could:

m.C1 = pyo.Constraint(expr=sum(m.x[i] for x in m.idx) == 100)

In general, when you are starting:

Add 1 thing to your model, and then print the model:

model.pprint()

See if it looks right, if not, fix it. Then repeat!