Multiplex stdout to a file

Tee.py

from traceback import print_exception


class Tee(object):
    """ Multiplex stdout to a file

    Possibly useful for inspecting the output of a long running python process started via IPython.

    Adapted from answers found in SO questions [1] and [2].

    [1] http://stackoverflow.com/questions/616645/how-do-i-duplicate-sys-stdout-to-a-log-file-in-python
    [2] http://stackoverflow.com/questions/14571090/ipython-redirecting-output-of-a-python-script-to-a-file-like-bash
    """

    def __init__(self, name, mode='w'):
        self.name = name
        self.mode = mode

    def __enter__(self):
        self.file_handle = open(self.name, self.mode)
        self.terminal = sys.stdout
        sys.stdout = self

    def __exit__(self, exc_type, exc_value, traceback):
        print_exception(exc_type, exc_value, traceback,
                        None, self.file_handle)
        self.flush()
        self.file_handle.close()
        sys.stdout = self.terminal

    def write(self, data):
        self.file_handle.write(data)
        self.terminal.write(data)
        self.flush()

    def flush(self):
        self.file_handle.flush()
        self.terminal.flush()


print 'Print only to stdout'


with Tee('tee.txt'):
    print 'Now print to both stdout and the tee-ed file'
    print '(Go tail -F this file already)'
    import time
    for i in range(5):
        print 'Output #{}'.format(i)
        time.sleep(0.5)
    raise ValueError('kthxbye')


for i in range(5):
    print 'Print only to stdout again'
    time.sleep(0.5)