# Write a context manager which temporarily replaces
# sys.stdout with a io.StringIO() object and thus
# captures the output of print().

import contextlib
import sys
import io

@contextlib.contextmanager
def capture_stdout():
    r"""Replace sys.stdout with String() for the block.

    >>> with capture_stdout() as out:
    ...     print('goo')
    >>> out.getvalue()
    'goo\n'
    """
    out = io.StringIO()
    old, sys.stdout = sys.stdout, out
    try:
        yield out
    finally:
        sys.stdout = old

# To test this file, use:
#  py.test-3.4 --doctest-modules capture_stdout.py
# or
#  python3 -m doctest capture_stdout.py