Controlling stdout/stderr from Jython

I am calling a function in a java library from jython which prints to stdout. I would like to suppress this output from the jython script. I attempt the python idiom replacing sys.stdout with a开发者_运维知识库 file like object (StringIO), but this does not capture the output of the java library. I'm guessing sys.stdout does not affect the java program. Is there a standard convention for redirecting or suppressing this output programatically in jython? If not what ways can I accomplish this?

You can use System.setOut, like this:

>>> from java.lang import System 
>>> from java.io import PrintStream, OutputStream
>>> oldOut = System.out
>>> class NoOutputStream(OutputStream):         
...     def write(self, b, off, len): pass      
... 
>>> System.setOut(PrintStream(NoOutputStream()))
>>> System.out.println('foo')                   
>>> System.setOut(oldOut)
>>> System.out.println('foo')                   
foo

Note that this won't affect Python output, because Jython grabs System.out when it starts up so you can reassign sys.stdout as you'd expect.

I've created a context manager to mimic (Python3's) contextlib's redirect_stdout (gist here):

'''Wouldn't it be nice if sys.stdout knew how to redirect the JVM's stdout? Shooting star.
        Author: Sean Summers <seansummers@gmail.com> 2015-09-28 v0.1
        Permalink: https://gist.githubusercontent.com/seansummers/bbfe021e83935b3db01d/raw/redirect_java_stdout.py
'''

from java import io, lang

from contextlib import contextmanager

@contextmanager
def redirect_stdout(new_target):
        ''' Context manager for temporarily redirecting sys.stdout to another file or file-like object
                see contextlib.redirect_stdout documentation for usage
        '''

        # file objects aren't java.io.File objects...
        if isinstance(new_target, file):
                new_target.close()
                new_target = io.PrintStream(new_target.name)
        old_target, target = lang.System.out, new_target
        try:
                lang.System.setOut(target)
                yield None
        finally:
                lang.System.setOut(old_target)