Managing Data in AbstractModelsΒΆ

There are roughly three ways of using data to construct a Pyomo model:

  1. use standard Python objects,
  2. initialize a model with data loaded with a DataPortal object, and
  3. load model data from a Pyomo data command file.

Standard Python data objects include native Python data types (e.g. lists, sets, and dictionaries) as well as standard data formats like numpy arrays and Pandas data frames. Standard Python data objects can be used to define constant values in a Pyomo model, and they can be used to initialize Set and Param components. However, initializing Set and Param components in this manner provides few advantages over direct use of standard Python data objects. (An import exception is that components indexed by Set objects use less memory than components indexed by native Python data.)

The DataPortal class provides a generic facility for loading data from disparate sources. A DataPortal object can load data in a consistent manner, and this data can be used to simply initialize all Set and Param components in a model. DataPortal objects can be used to initialize both concrete and abstract models in a uniform manner, which is important in some scripting applications. But in practice, this capability is only necessary for abstract models, whose data components are initialized after being constructed. (In fact, all abstract data components in an abstract model are loaded from DataPortal objects.)

Finally, Pyomo data command files provide a convenient mechanism for initializing Set and Param components with a high-level data specification. Data command files can be used with both concrete and abstract models, though in a different manner. Data command files are parsed using a DataPortal object, which must be done explicitly for a concrete model. However, abstract models can load data from a data command file directly, after the model is constructed. Again, this capability is only necessary for abstract models, whose data components are initialized after being constructed.

The following sections provide more detail about how data can be used to initialize Pyomo models.