Cplex Python如何避免打印输出

Question

after setting the objective function and constraints, i use

prob.solve()
print prob.solution.get_objective_value()

actually, I just want to print the objective value, however, it displays a lot of information of cplex,

Tried aggregator 1 time.
LP Presolve eliminated 5 rows and 1 columns.
All rows and columns eliminated.
Presolve time = -0.00 sec. (0.00 ticks)
0.5

I just want to display the last line 0.5, how to avoid printing other information by Cplex? Thank you in advance.

Answer 1

cplex specifies 3 output streams: log, error, warning and results. You can disable the output with the commands. set_xxx_stream(None). In your example,

prob.set_log_stream(None)
prob.set_error_stream(None)
prob.set_warning_stream(None)
prob.set_results_stream(None)

will disable all output. You can also specify an output file, instead of None. There are also several parameters that you can set to control the verbosity of the cplex output, but this is the best way to prevent cplex from printing anything.

Answer 2

You can adjust the verbosity level using the mip.display parameter:

# where c is a Cplex object
c.parameters.mip.display.set(0)

See here for more info.

Answer 3

Try this:

 ans = prob.solution.get_objective_value()
 print ans.split('\n')[-1]

Since Cplex is commercial I can't test if my solution is working. But you get the idea: split the string, get only what you want.