How to redirect python warnings to a custom stream?

Question

Let's say I have a file-like object like StreamIO and want the python's warning module write all warning messages to it. How do I do that?

Answer 1

Try reassigning warnings.showwarning i.e.

#!/sw/bin/python2.5

import warnings, sys

def customwarn(message, category, filename, lineno, file=None, line=None):
    sys.stdout.write(warnings.formatwarning(message, category, filename, lineno))

warnings.showwarning = customwarn
warnings.warn("test warning")

will redirect all warnings to stdout.

Answer 2

I think something like this would work, although it's untested code and the interface looks like there is a cleaner way which eludes me at present:

import warnings

# defaults to the 'myStringIO' file
def my_warning_wrapper(message, category, filename, lineno, file=myStringIO, line=None):
    warnings.show_warning(message, category, filename, lineno, file, line)    

warnings._show_warning = my_warning_wrapper

A look inside Lib\warnings.py should help put you on the right track if that isn't enough.

Answer 3

import sys
import StringIO

sys.stdout = StringIO.StringIO()