How to duplicate sys.stdout to a log file?

Question

Edit: Since it appears that there\'s either no solution, or I\'m doing something so non-standard that nobody knows - I\'ll revise my question to also ask: What is the best w

Answer 1

Here is another solution, which is more general than the others -- it supports splitting output (written to sys.stdout) to any number of file-like objects. There's no requirement that __stdout__ itself is included.

import sys

class multifile(object):
    def __init__(self, files):
        self._files = files
    def __getattr__(self, attr, *args):
        return self._wrap(attr, *args)
    def _wrap(self, attr, *args):
        def g(*a, **kw):
            for f in self._files:
                res = getattr(f, attr, *args)(*a, **kw)
            return res
        return g

# for a tee-like behavior, use like this:
sys.stdout = multifile([ sys.stdout, open('myfile.txt', 'w') ])

# all these forms work:
print 'abc'
print >>sys.stdout, 'line2'
sys.stdout.write('line3\n')

NOTE: This is a proof-of-concept. The implementation here is not complete, as it only wraps methods of the file-like objects (e.g. write), leaving out members/properties/setattr, etc. However, it is probably good enough for most people as it currently stands.

What I like about it, other than its generality, is that it is clean in the sense it doesn't make any direct calls to write, flush, os.dup2, etc.