#!/bin/env python

import xpress as xp

p = xp.problem ()

# fill in a problem with three variables and four constraints

p.loadproblem ("",                                            # probname
               ['G','G','E', 'L'],                            # qrtypes
               [-2.4, -3, 4, 5],                              # rhs
               None,                                          # range
               [3,4,5],                                       # obj
               [0,2,4,8],                                     # mstart
               None,                                          # mnel
               [0,1,2,3,0,1,2,3],                             # mrwind
               [1,1,1,1,1,1,1,1],                             # dmatval
               [-1,-1,-1],                                    # lb
               [3,5,8],                                       # ub
               colnames = ['x1','x2','x3'],                   # column names
               rownames = ['row1','row2','row3','constr_04']) # row    names

p.write ("loadlp", "lp")
p.solve ()

# Create another variable and add it, then modify the objective
# function. Note that the objective function is replaced by, not
# amended with, the new objective

x = xp.var()
p.addVariable (x)
p.setObjective (x**2 + 2*x + 444)
p.solve()
p.write ("updated", "lp")