gurobipy.SOS#

class SOS#

Gurobi SOS constraint object. SOS constraints are always associated with a particular model. You create an SOS object by adding an SOS constraint to a model (using Model.addSOS), rather than by using an SOS constructor. Similarly, SOS constraints are removed using the Model.remove method.

An SOS constraint can be of type 1 or 2 (GRB.SOS_TYPE1 or GRB.SOS_TYPE2). A type 1 SOS constraint is a set of variables where at most one variable in the set may take a value other than zero. A type 2 SOS constraint is an ordered set of variables where at most two variables in the set may take non-zero values. If two take non-zero values, they must be contiguous in the ordered set.

SOS constraint objects have a number of attributes, e.g., IISSOS, which can be queried with the SOS.getAttr method.

The full list of attributes can be found in the Attributes section of this document. Examples of how to query and set attributes can also be found in this section.

getAttr(attrname)#

Query the value of an SOS attribute.

Raises an AttributeError if the requested attribute doesn’t exist or can’t be queried. Raises a GurobiError if there is a problem with the SOS object (e.g., it was removed from the model).

Parameters:

attrname – The attribute being queried.

Returns:

The current value of the requested attribute.

Example:
print(sos.getAttr(GRB.Attr.IISSOS))
setAttr(attrname, newvalue)#

Set the value of an SOS attribute. Note that, due to our lazy update approach, the change won’t actually take effect until you update the model (using Model.update), optimize the model (using Model.optimize), or write the model to disk (using Model.write).

Raises an AttributeError if the specified attribute doesn’t exist or can’t be set. Raises a GurobiError if there is a problem with the SOS object (e.g., it was removed from the model).

Parameters:

  • attrname – The attribute being modified.

  • newvalue – The desired new value of the attribute.

Example:
sos.setAttr(GRB.Attr.IISSOSForce, 1)
var.setAttr("IISSOSForce", 0.0)