Pulp linear-program

#!/usr/bin/env python

from pulp import *
import sys

x = []
thismodule = sys.modules[__name__]

for i in range(8):
    name = 'x{0}'.format(i)
    var = LpVariable(name, 0, None)
    setattr(thismodule, name, var)
    x.append(var)

# defines the problem
prob = LpProblem("problem", LpMinimize)

# defines the constraints
prob += (+1.0 * x0) + (+1.0 * x1) + (+1.0 * x2) + (+1.0 * x3) + (+0.0 * x4) + (+0.0 * x5) + (+0.0 * x6) + (+0.0 * x7) == 40
prob += (+0.0 * x0) + (+0.0 * x1) + (+0.0 * x2) + (+0.0 * x3) + (+1.0 * x4) + (+1.0 * x5) + (+1.0 * x6) + (+1.0 * x7) == 40
prob += (+0.0 * x0) + (+1.0 * x1) + (-1.0 * x2) + (+0.0 * x3) + (+0.0 * x4) + (+1.0 * x5) + (-1.0 * x6) + (+0.0 * x7) == 0

prob += (+1.0 * x0) + (+0.0 * x1) + (+0.0 * x2) + (+0.0 * x3) + (+1.0 * x4) + (+0.0 * x5) + (+0.0 * x6) + (+0.0 * x7) <= 20
prob += (-1.0 * x0) + (-0.0 * x1) + (-0.0 * x2) + (-0.0 * x3) + (-1.0 * x4) + (-0.0 * x5) + (-0.0 * x6) + (-0.0 * x7) <= -10
prob += (-0.0 * x0) + (-1.0 * x1) + (-0.0 * x2) + (-0.0 * x3) + (-0.0 * x4) + (-1.0 * x5) + (-0.0 * x6) + (-0.0 * x7) <= 0
prob += (-0.0 * x0) + (-0.0 * x1) + (-1.0 * x2) + (-0.0 * x3) + (-0.0 * x4) + (-0.0 * x5) + (-1.0 * x6) + (-0.0 * x7) <= 0
prob += (-0.0 * x0) + (-0.0 * x1) + (-0.0 * x2) + (-1.0 * x3) + (-0.0 * x4) + (-0.0 * x5) + (-0.0 * x6) + (-1.0 * x7) <= 0

for i in x:
    prob += i >= 0

# defines the objective function to maximize
prob += (-8 * x0) + (+0 * x1) + (+0 * x2) + (-1 * x3) + \
        (-4 * x4) + (-6 * x5) + (-4 * x6) + (-1 * x7)

# solve the problem
status = prob.solve(GLPK(msg=0))

# print the results x1 = 20, x2 = 60
print '\n'.join(['x_{0} = {1}'.format(i, value(v)) for i, v in enumerate(x)])