Python：如何从子流程的stdout流式传输

Question

我的目标是实现一个小的Python书面脚本，以使我更轻松地处理Jupyter。

因此我编写了此脚本：

import signal
import socket
import subprocess
import sys

sp = None
port = 8888


def get_own_ip():
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    try:
        s.connect(('1.1.1.1', 1))
        IP = s.getsockname()[0]
    except:
        IP = '127.0.0.1'
    finally:
        s.close()
    return IP


def signal_handler(sig, frame):
    # terminates Jupyter by sending two SIGINTs to it
    if sp is not None:
        # send termination to jupyter
        sp.send_signal(signal.SIGINT)
        sp.send_signal(signal.SIGINT)

        sys.exit(0)


if __name__ == "__main__":

    own_ip = get_own_ip()

    sp = subprocess.Popen(["jupyter-notebook"
                           , "--ip='%s'" % own_ip
                           , "--port=%i" % port
                           , "--no-browser"],
                          stdout=subprocess.PIPE,
                          stdin=subprocess.PIPE,
                          bufsize=1)

    print(sp)

    signal.signal(signal.SIGINT, signal_handler)

    with sp.stdout:
        print('read')
        for line in sp.stdout.readline():
            print('line: %s' % line)
    print('wait')
    sp.wait()  # wait for the subprocess to exit

首先，我检索我的IP地址，以将其用作Jupyter的参数。然后我运行Jupyter，然后我想在Jupyter运行时过滤Jupyter（stdout）的一些输出。但是，似乎sp.stdout.readline()处于阻止状态。

上面的代码向终端产生以下输出：

/usr/bin/python3.6 /home/alex/.scripts/get_own_ip.py
<subprocess.Popen object at 0x7fa956374240>
read
[I 22:43:31.611 NotebookApp] Serving notebooks from local directory: /home/alex/.scripts
[I 22:43:31.611 NotebookApp] The Jupyter Notebook is running at:
[I 22:43:31.611 NotebookApp] http://192.168.18.32:8888/?token=c4b7784d784206fc357b8f484b8d659fed6a2b1733b46ae6
[I 22:43:31.611 NotebookApp]  or http://127.0.0.1:8888/?token=c4b7784d784206fc357b8f484b8d659fed6a2b1733b46ae6
[I 22:43:31.611 NotebookApp] Use Control-C to stop this server and shut down all kernels (twice to skip confirmation).
[C 22:43:31.614 NotebookApp] 

    To access the notebook, open this file in a browser:
        file:///home/alex/.local/share/jupyter/runtime/nbserver-18280-open.html
    Or copy and paste one of these URLs:
        http://192.168.18.32:8888/?token=c4b7784d784206fc357b8f484b8d659fed6a2b1733b46ae6
     or http://127.0.0.1:8888/?token=c4b7784d784206fc357b8f484b8d659fed6a2b1733b46ae6

您可以看到发生了输出，但不会被sp.stdout.readline()识别。

如何正确地从sp.stdout流式播放？

Answer 1

我认为这些消息是写到stderr而不是stdout的。因此，您需要改用sp.stderr。

您可以在shell中运行它（如果您使用的是Linux，可以测试这种情况：

jupyter notebook > stdout.log 2> stderr.log