Is there a way to get a list with variable names in Pyomo?

Question

I wanna append all of my integer-bounded variables into the integer_constraints_list that i've defined. Is there a way to get some sort of list or array with all of my variable names to iterate over the code i made using a for loop? something like variables_list = [inst.x[i], inst.y[i], inst.z[i]].

I know there is something of the sort for pyomo kernel, but i used environ to define the model

model.I = RangeSet(1,20)
model.x = Var(model.I, domain=NonNegativeIntegers)
model.y = Var(model.I, domain=NonPositiveIntegers)
model.z = Var(model.I, domain=NonPositiveIntegers)

inst = model.create_instance(data)
integer_constraints_list = []

for i in inst.I:
     if "nonnegativeintegers" in str(inst.x[i].domain).lower():
          integer_constraints_list.append(inst.x[i])
          inst.x[i].domain = NonNegativeReals

to something like

variables_list = [inst.x[i], inst.y[i], inst.z[i]]
for v in variables_list:
     for i in inst.I:
          if "nonnegativeintegers" in str(v.domain).lower():
               integer_constraints_list.append(v[i])
               v.domain = NonNegativeReals

score 0 · Answer 1 · answered Nov 28 '19 at 22:23

0

you can do something like this:

variables_list = ['inst.x', 'inst.y', 'inst.z']
for v in variables_list:
     for i in inst.I:
          if "nonnegativeintegers" in str(vars()[v][i].domain).lower():
               integer_constraints_list.append(v[i])
               vars()[v][i].domain = NonNegativeReals

answered Nov 28 '19 at 22:23

prhmma

843
10
18

didn't work :( it seems there are no keys with those names stored – Pablo Pablo Nov 28 '19 at 23:32

score 0 · Answer 2 · answered Nov 28 '19 at 23:34

welp, the solution was not nearly as complex as i thought

variables_list = [inst.x, inst.y, inst.z]
for v in variables_list:
    for i in inst.I:
        if "nonnegativeintegers" in str(v[i].domain).lower():
           integer_constraints_list.append(v[i])
           v[i].domain = NonNegativeReals

score 0 · Accepted Answer · answered Nov 29 '19 at 20:49

I would suggest doing a domain equality comparison rather than a comparison on the string representation:

integer_vars = [v for v in inst.component_data_objects(Var) if v.domain == NonNegativeIntegers]
integer_constraints_list.extend(integer_vars)
for v in integer_vars:
    v.domain = NonNegativeReals

Is there a way to get a list with variable names in Pyomo?

3 Answers3