Optimizer controls in Python

The reference documentation for xpress.problem.setControl() says:

setControl(...)
    Purpose: 
    Sets one or more controls of a problem.
    
    Synopsis:
    
    problem.setControl(string, value)
    
    Example: 
    p = xpress.problem()
    p.setControl('miprelstop', 1e-4)
    p.setControl({'feastol': 1e-4, 'presolve': 0})
    
    Further information:
    ...
    2.  
    This function can be used in two ways depending on whether one wants
    to set one or more controls. In the first case, the arguments form a
    pair (string, value) where the first element is the lower-case name of
    a control (see the Xpress Optimizer reference manual for a complete
    list of controls). In the second case, the argument is a Python
    dictionary whose keys are control name string and whose values
    are the value of the control.

So the names of controls used in the Python interface are the lower-case names (without the XPRS_ prefix).

The same naming convention applies when referring to controls as object members.

This is explained in the user manual here and here.