python popen.stdout.readline() 卡住

Question

我遇到一个问题……有没有人知道为什么这段代码在while循环里卡住了？这个循环似乎没有处理到stdout的最后一行。

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()

当遇到readline()时，脚本就卡住了，光标一直在闪烁。我不明白为什么。有没有人能帮我解释一下？

Answer 1

你在做非阻塞读取的时候，有帮助吗？

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()

我不太确定你具体想要做什么，但这样做会不会更好呢？它会一次性读取所有数据，而不是每次只读取一行。对我来说，这样看起来更容易理解。

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)

补充：这是一个更通用的脚本，应该更适合你的使用场景：

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)