Question

In python, is there an easy way to set up a file-like object for writing that is actually backed by multiple output streams? For instance, I want something like this:

file1 = open("file1.txt", "w")
file2 = open("file2.txt", "w")
ostream = OStreamWrapper(file1, file2, sys.stdout)

#Write to both files and stdout at once:
ostream.write("ECHO!")

So what I’m looking for is OStreamWrapper. I know it’d be pretty easy to write my own, but if there’s an existing one, I’d rather use that and not have to worry about finding and covering edge cases.

Answer 1

Way to wrap all public file functions:

import sys

def _call_for_all_streams(func_name):
    def wrapper(self, *args, **kwargs):
        result = []
        for stream in self._streams:
            func = getattr(stream, func_name)
            result.append(func(*args, **kwargs))
        return result
    return wrapper

class OStreamWrapper(object):
    def __init__(self, *streams):
        self._streams = streams

for method in filter(lambda x: not x.startswith('_'), dir(file)):
    setattr(OStreamWrapper, method, _call_for_all_streams(method))

if __name__ == '__main__':
    file1 = open("file1.txt", "w")
    file2 = open("file2.txt", "w")
    ostream = OStreamWrapper(file1, file2, sys.stdout)
    ostream.write("ECHO!")
    ostream.close()

But it’s kinda dirty.