PyMathProg Git

import csv
dists = csv.reader(open('capdist.csv'), 'excel')
dm = [[int(k) for k in t[2:33]] 
     for t in dists if t[1]]

n = len(dm) #how many cities
V = range(n)
E = [(i,j) for i in V for j in V if i!=j]

print "there are %d cities"%n

from pymprog import *
beginModel('ChinaCapitalCitiesTSP')
x = var('x', E, bool)
minimize( sum(dm[i][j]*x[i,j] for i,j in E), 'TravelDist' )
st([sum( x[k,j] for j in V if j!=k ) == 1 for k in V], 'leave')
st([sum( x[i,k] for i in V if i!=k ) == 1 for k in V], 'enter')

y = var('y', E)
st([(n-1)*x[t] >= y[t] for t in E], 'cap')
st([sum(y[i,k] for i in V if i!=k) + (0 if k else n)
==sum(y[k,j] for j in V if j!=k) + 1 for k in V], 'sale')

solve(float)
print "simplex done:", status()
solvopt(integer='advanced')
solveMIP() #solve the IP problem

print "Optimal tour length:", vobj()
tour = [t for t in E if x[t].primal>.5]
cat = 0
print("This is the optimal tour:")
for k in V: 
   print cat+1, '->',
   for i,j in tour: 
      if i==cat: cat=j; break
print cat+1