nonblocking read function for python, e.g. for named pipes

read_nonblocking.py

def read_nonblocking(path, bufferSize=100, timeout=.100):
    import time
    """
    implementation of a non-blocking read
    works with a named pipe or file

    errno 11 occurs if pipe is still written too, wait until some data
    is available
    """
    grace = True
    result = []
    try:
        pipe = os.open(path, os.O_RDONLY | os.O_NONBLOCK)
        while True:
            try:
                buf = os.read(pipe, bufferSize)
                if not buf:
                    break
                else:
                    content = buf.decode("utf-8")
                    line = content.split("\n")
                    result.extend(line)
            except OSError as e:
                if e.errno == 11 and grace:
                    # grace period, first write to pipe might take some time
                    # further reads after opening the file are then successful
                    time.sleep(timeout)
                    grace = False
                else:
                    break

    except OSError as e:
        if e.errno == errno.ENOENT:
            pipe = None
        else:
            raise e

    return result