amphibians_coexistence_model.py

from __future__ import print_function
from ortools.linear_solver import pywraplp

def solve_coexistence():

  t = 'Amphibian coexistence'
  s = pywraplp.Solver(t,pywraplp.Solver.GLOP_LINEAR_PROGRAMMING)
  #def NumVar(self, lower_bound: "double", upperbound: "double", name: "std::string const &")
  x = [s.NumVar(0,1000,'x[%i]' % i) for i in range(3)]
  pop = s.NumVar(0,3000,'pop')
  s.Add(2*x[0] + x[1] + x[2] <= 1500)
  s.Add(x[0] + 3*x[1] + 2*x[2] <= 3000)
  s.Add(x[0] + 2*x[1] + 3*x[2] <= 4000)
  s.Add(pop == x[0] + x[1] + x[2])
  s.Maximize(pop)
  s.Solve()
  return pop.SolutionValue(),[e.SolutionValue() for e in x]


if __name__ == '__main__':

  pop,x = solve_coexistence()

  T=[['Specie', 'Count']]

  for i in range(3):
    T.append([['Toads','Salamanders','Caecilians'][i], x[i]])

  print(T)

  T.append(['Total', pop])

  for e in T:
    print (e[0],e[1])