Pipe context manager.

pipe_context.py

import os
from contextlib import contextmanager


@contextmanager
def pipe(my_end):
    """
    Context manager that produces a unidirectional pipe, automatically always
    closing the other end of that pipe. Useful for creating pipes to use with
    subprocesses.

    If ``my_end`` is ``"r"``, then the write end of the pipe is always closed.
    The read end is always closed if ``my_end`` is ``"w"``.

    Yields ``(read_fd, write_fd)`` to the context.

    """
    r, w = os.pipe()
    try:
        yield r, w
    finally:
        os.close(r if my_end == "r" else w)