Originally posted by: gioker

The documentation for the python interface to Cplex states:

>>> 
import cplex

>>> c = cplex.Cplex()

>>> c.variables.add(names = [
"x1", 
"x2", 
"x3"])

>>> c.linear_constraints.add(lin_expr = [cplex.SparsePair(ind = [
"x1", 
"x3"], val = [1.0, -1.0]),
 
                                    cplex.SparsePair(ind = ["x1", "x2"], val = [1.0, 1.0]),
 
                                    cplex.SparsePair(ind = ["x1", "x2", "x3"], val = [-1.0] * 3),
 
                                    cplex.SparsePair(ind = ["x2", "x3"], val = [10.0, -2.0])],
 
                            senses = ["E", "L", "G", "R"],
 
                            rhs = [0.0, 1.0, -1.0, 2.0],
 
                            range_values = [0.0, 0.0, 0.0, -10.0],
 
                            names = ["c0", "c1", "c2", "c3"],)

>>> c.linear_constraints.get_rhs()

[0.0, 1.0, -1.0, 2.0]

but it returns the following error:

  File "findsol.py", line 98, in <module>
    findsol(n_sol)
  File "findsol.py", line 50, in findsol
    names = ["c0", "c1", "c2", "c3"],)
  File "/Library/Python/2.7/site-packages/cplex/_internal/_subinterfaces.py", line 1187, in add
    rmat = _C_HBMatrix(lin_expr, self._cplex._env_lp_ptr, 0, self._env.parameters.read.apiencoding.get())
  File "/Library/Python/2.7/site-packages/cplex/_internal/_matrices.py", line 74, in __init__
    raise TypeError(" invalid matrix input type -- ", self._mat[0])
TypeError: (' invalid matrix input type -- ', u'x1')

I have a Mac with the latest releases of both Python and Cplex.

Thanks.

Originally posted by: gioker

Found the problem. 

At the beginning of the code I forgot I added:

from __future__ import unicode_literals

Once removed the problem was gone. Of course, an other solution would be  *.encode('UTF-8').