Supress cpymad output to stdio

[mabl]

When doing parameter sweeps, the output of madx pollutes the standard output.
I have looked and found no way in the documentation to suppress or redirect that output.

[coldfix]

Hey,

redirecting the MAD-X output to an arbitrary file handle can be achieved as follows:

from cpymad.madx import Madx
from cpymad import _rpc
import subprocess
import os

def madx_redirect_stdio(stdout=subprocess.STDOUT, stderr=subprocess.STDOUT):
        with open(os.devnull, 'r') as devnull:
            client, process = _rpc.LibMadxClient.spawn_subprocess(
                stdout=stdout,
                stderr=stderr,
                stdin=devnull,
                bufsize=0)         # unbuffered IO
        return Madx(libmadx=client.libmadx)

# drop all stdio:
devnull = open(os.devnull, 'w')
madx = madx_redirect_stdio(devnull, devnull)

See also the code in MadGUI.

I admit, this is a bit hacky and the documentation is almost nonexisting. Probably its a common demand and should be made easier or at least documented. I'll try to add something as soon as I get some time (currently busy with something else, sorry).

Hope, this helps.

EDIT Sorry, had to correct some minor inconsistencies in the original code.

[coldfix]

I guess I will patch the Madx constructor so that it accepts and forwards keyword arguments stdout and stderr. Hope I get it done by the end of this week.

[coldfix]

Okay, took me a bit longer to find some time to do this. You can now simply do

m = Madx(stdout=False)

# or

with open('log.txt', 'w') as f:
    m = Madx(stdout=f)

I uploaded a new release on PyPI. Let me know if you have any problems.

Best regards,
Thomas

[mabl]

Thanks! That works great for me!