#!/usr/bin/env python3.7

# Copyright 2023, Gurobi Optimization, LLC

# This example reads an LP model from a file and solves it.
# If the model is infeasible or unbounded, the example turns off
# presolve and solves the model again. If the model is infeasible,
# the example computes an Irreducible Inconsistent Subsystem (IIS),
# and writes it to a file

import sys
import gurobipy as gp
from gurobipy import GRB

if len(sys.argv) < 2:
    print('Usage: lp.py filename')

# Read and solve model

model = gp.read(sys.argv[1])

if model.Status == GRB.INF_OR_UNBD:
    # Turn presolve off to determine whether model is infeasible
    # or unbounded
    model.setParam(GRB.Param.Presolve, 0)

if model.Status == GRB.OPTIMAL:
    print('Optimal objective: %g' % model.ObjVal)
elif model.Status != GRB.INFEASIBLE:
    print('Optimization was stopped with status %d' % model.Status)

# Model is infeasible - compute an Irreducible Inconsistent Subsystem (IIS)

print('Model is infeasible')
print("IIS written to file 'model.ilp'")

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