Here is the code that I run in VS Code (which runs fine in a Google Colab notebook) and the error message that I get when running in VS Code. I included my import statement that was run in a previous cell.
from amplpy import AMPL, tools
ampl = tools.ampl_notebook(modules=[“cplex”], license_uuid=“default”)
#Transshipment Problem
%%writefile transshipment_model.mod
set S = {“A”, “B”, “C”}; #Supply nodes
set D = {“W”, “X”, “Y”, “Z”}; #Demand nodes
set T = {“D”, “E”}; #Transshipment nodes
set Cities = {‘A’, ‘B’, ‘C’, ‘D’, ‘E’, ‘W’, ‘X’, ‘Y’, ‘Z’}; # set of all cities
param Supply{S}; # Supply capacity of supply nodes
param Demand{D}; # Demand at demand nodes
param C{Cities,Cities}; # Cost matrix
var x{Cities,Cities} >= 0; # Amount shipped between nodes
# Objective: Minimize total transportation cost
minimize Z: sum {i in Cities, j in Cities} C[i,j] * x[i,j];
# Supply constraints
s.t. supply{i in S}: sum {j in Cities} x[i,j] >= Supply[i];
# Demand constraints
s.t. demand{j in D}: sum {i in Cities} x[i,j] <= Demand[j];
# Transshipment constraints
s.t. transshipment{j in T}: sum {i in S} x[i,j] - sum {i in D} x[j,i] = 0;
Cell In[2], line 4
set S = {“A”, “B”, “C”}; #Supply nodes
^
SyntaxError: invalid syntax
I can’t figure out why it continues to give me this error in VS Code.