Gurobi tuple dict. This is a sub-class of the Python dict class that is designed to efficiently support a usage pattern that is quite common when building optimization models. In particular, a tupledict is a Python dict where the keys are stored as a Gurobi tuplelist, and where the values are typically Gurobi Var objects. Objects of this class make it easier to build linear expressions on sets of Gurobi variables, using tuplelist.select() syntax and semantics.

You typically build a tupledict by calling Model.addVars. Once you've created a tupledict d, you can use d.sum() to create a linear expression that captures the sum of the variables in the tupledict. You can also use a command like d.sum(1, '*', 5) to create a sum over a subset of the variables in d. Assuming the keys for the tupledict are tuples containing three fields, this statement would create a linear expression that captures the sum over all variables in d whose keys contain a 1 in the first field of the tuple and a 5 in the third field (the '*' character is a wildcard that indicates that any value is acceptable in that field). You can also use d.prod(coeff) to create a linear expression where the coefficients are pulled from the argument dict. For example, if d(1,2,5) contains variable x and coeff(1,2,5) is 2.0, then the resulting expression would include term <span>$</span>2.0*x<span>$</span>.

To access the members of a tupledict, you can use standard dict indexing. For example, d[1,2] returns the value associated with tuple (1,2).

Note that a tupledict key must be a tuple of scalar values (int, float, string, ...). Thus, you can use (1, 2.0, 'abc') as a key, but you can't use ((1, 2.0), 'abc').

Note that tupledict objects build and maintain a set of internal data structures to support efficient select operations. If you wish to reclaim the storage associated with these data structures, you can call the clean function.