python popen.stdout.readline()挂起 [英] python popen.stdout.readline() hangs

问题描述

我有问题...没有人知道为什么这段代码在while循环中挂起.循环似乎没有捕捉到stdout的最后一行.

Im having a problem... does anyone knows why this code hangs in the while loop. The loop doesn't seem to catch the last line of the stdout.

working_file = subprocess.Popen(["/pyRoot/iAmACrashyProgram"], stdout=subprocess.PIPE, stdin=subprocess.PIPE, stderr=subprocess.PIPE)

line = working_file.stdout.readline()
working_file.stdout.flush()
while working_file != "" :
    print(line)
    line = working_file.stdout.readline()
    working_file.stdout.flush()

遇到readline()时，脚本随光标一起挂起，只是闪烁.我不明白为什么.谁能给我一些启示

the script hangs with the curser just blinking when readline() is encountered. I dont understand why. can anyone shed some light

谢谢

乔恩

推荐答案

进行无阻塞读取是否对您有帮助?

Does doing a nonblocking read help you out?

import fcntl
import os

def nonBlockReadline(output):
    fd = output.fileno()
    fl = fcntl.fcntl(fd, fcntl.F_GETFL)
    fcntl.fcntl(fd, fcntl.F_SETFL, fl | os.O_NONBLOCK)
    try:
        return output.readline()
    except:
        return ''

working_file = subprocess.Popen(["/pyRoot/iAmACrashyProgram"], stdout=subprocess.PIPE, stdin=subprocess.PIPE, stderr=subprocess.PIPE)

line = nonBlockReadline(working_file.stdout)
working_file.stdout.flush()
while working_file != "" :
    print(line)
    line = nonBlockReadline(working_file.stdout)
    working_file.stdout.flush()

我不确定您要做什么，但是这样做会更好吗?它只读取所有数据，而不是一次只读取一行.对我来说，它更具可读性.

I'm not sure exactly what you're trying to do, but will this work better? It just reads all the data, instead of reading only one line at a time. It's a little more readable to me.

import fcntl
import os

def nonBlockRead(output):
    fd = output.fileno()
    fl = fcntl.fcntl(fd, fcntl.F_GETFL)
    fcntl.fcntl(fd, fcntl.F_SETFL, fl | os.O_NONBLOCK)
    try:
        return output.read()
    except:
        return ''

working_file = subprocess.Popen(["/pyRoot/iAmACrashyProgram"], stdout=subprocess.PIPE, stdin=subprocess.PIPE, stderr=subprocess.PIPE)

stdout = ''

while working_file.poll() is None:
    stdout += nonBlockRead(working_file.stdout)

# we can probably save some time and just print it instead...
#print(stdout)

stdout = stdout.splitlines()
for line in stdout:
    print(line)

应该更适合您的用例的通用脚本:

A generalized script which should be more suited for your use case:

import fcntl
import os

def nonBlockRead(output):
    fd = output.fileno()
    fl = fcntl.fcntl(fd, fcntl.F_GETFL)
    fcntl.fcntl(fd, fcntl.F_SETFL, fl | os.O_NONBLOCK)
    try:
        return output.read()
    except:
        return ''

working_file = subprocess.Popen(["/pyRoot/iAmACrashyProgram"], stdout=subprocess.PIPE, stdin=subprocess.PIPE, stderr=subprocess.PIPE)

while working_file.poll() is None:
    stdout = nonBlockRead(working_file.stdout)

    # make sure it returned data
    if stdout:
        # process data
        working_file.stdin.write(something)

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