def setup_kernel(cmd): """start an embedded kernel in a subprocess, and wait for it to be ready Returns ------- kernel_manager: connected KernelManager instance """ kernel = Popen([sys.executable, '-c', cmd], stdout=PIPE, stderr=PIPE, env=env) connection_file = os.path.join(IPYTHONDIR, 'profile_default', 'security', 'kernel-%i.json' % kernel.pid ) # wait for connection file to exist, timeout after 5s tic = time.time() while not os.path.exists(connection_file) \ and kernel.poll() is None \ and time.time() < tic + SETUP_TIMEOUT: time.sleep(0.1) if kernel.poll() is not None: o,e = kernel.communicate() e = py3compat.cast_unicode(e) raise IOError("Kernel failed to start:\n%s" % e) if not os.path.exists(connection_file): if kernel.poll() is None: kernel.terminate() raise IOError("Connection file %r never arrived" % connection_file) client = BlockingKernelClient(connection_file=connection_file) client.load_connection_file() client.start_channels() client.wait_for_ready() try: yield client finally: client.stop_channels() kernel.terminate()