下面是运行任意命令返回其标准输出数据的Python代码,或在非零退出码上引发异常:
proc = subprocess.Popen(
cmd,
stderr=subprocess.STDOUT, # Merge stdout and stderr
stdout=subprocess.PIPE,
shell=True)
communication用于等待进程退出:
stdoutdata, stderrdata = proc.communicate()
子进程模块不支持超时——杀死运行超过X秒的进程的能力——因此,通信可能需要很长时间才能运行。
在Windows和Linux上运行的Python程序中实现超时的最简单方法是什么?
我有一个问题,我想终止一个多线程子进程,如果它花费的时间超过给定的超时长度。我想在Popen()中设置一个超时,但它不起作用。然后,我意识到Popen().wait()等于call(),所以我有了在.wait(timeout=xxx)方法中设置超时的想法,这最终工作了。因此,我是这样解决的:
import os
import sys
import signal
import subprocess
from multiprocessing import Pool
cores_for_parallelization = 4
timeout_time = 15 # seconds
def main():
jobs = [...YOUR_JOB_LIST...]
with Pool(cores_for_parallelization) as p:
p.map(run_parallel_jobs, jobs)
def run_parallel_jobs(args):
# Define the arguments including the paths
initial_terminal_command = 'C:\\Python34\\python.exe' # Python executable
function_to_start = 'C:\\temp\\xyz.py' # The multithreading script
final_list = [initial_terminal_command, function_to_start]
final_list.extend(args)
# Start the subprocess and determine the process PID
subp = subprocess.Popen(final_list) # starts the process
pid = subp.pid
# Wait until the return code returns from the function by considering the timeout.
# If not, terminate the process.
try:
returncode = subp.wait(timeout=timeout_time) # should be zero if accomplished
except subprocess.TimeoutExpired:
# Distinguish between Linux and Windows and terminate the process if
# the timeout has been expired
if sys.platform == 'linux2':
os.kill(pid, signal.SIGTERM)
elif sys.platform == 'win32':
subp.terminate()
if __name__ == '__main__':
main()
对于python 2.6+,使用gevent
from gevent.subprocess import Popen, PIPE, STDOUT
def call_sys(cmd, timeout):
p= Popen(cmd, shell=True, stdout=PIPE)
output, _ = p.communicate(timeout=timeout)
assert p.returncode == 0, p. returncode
return output
call_sys('./t.sh', 2)
# t.sh example
sleep 5
echo done
exit 1
一旦你理解了在*unix中运行机器的整个过程,你将很容易找到更简单的解决方案:
考虑这个简单的例子,如何使用select.select()(现在几乎在*nix上随处可见)创建可超时的communication()冰毒。这也可以用epoll/poll/kqueue来编写,但select.select()变体可能是一个很好的例子。select.select()的主要限制(速度和1024 max fds)不适用于您的任务。
它在*nix下工作,不创建线程,不使用信号,可以从任何线程启动(不仅仅是主线程),并且足够快,可以从我机器上的stdout读取250mb/s的数据(i5 2.3ghz)。
在通信结束时连接stdout/stderr时出现问题。如果你有大量的程序输出,这可能会导致大量的内存使用。但是您可以多次调用communication(),超时时间较小。
class Popen(subprocess.Popen):
def communicate(self, input=None, timeout=None):
if timeout is None:
return subprocess.Popen.communicate(self, input)
if self.stdin:
# Flush stdio buffer, this might block if user
# has been writing to .stdin in an uncontrolled
# fashion.
self.stdin.flush()
if not input:
self.stdin.close()
read_set, write_set = [], []
stdout = stderr = None
if self.stdin and input:
write_set.append(self.stdin)
if self.stdout:
read_set.append(self.stdout)
stdout = []
if self.stderr:
read_set.append(self.stderr)
stderr = []
input_offset = 0
deadline = time.time() + timeout
while read_set or write_set:
try:
rlist, wlist, xlist = select.select(read_set, write_set, [], max(0, deadline - time.time()))
except select.error as ex:
if ex.args[0] == errno.EINTR:
continue
raise
if not (rlist or wlist):
# Just break if timeout
# Since we do not close stdout/stderr/stdin, we can call
# communicate() several times reading data by smaller pieces.
break
if self.stdin in wlist:
chunk = input[input_offset:input_offset + subprocess._PIPE_BUF]
try:
bytes_written = os.write(self.stdin.fileno(), chunk)
except OSError as ex:
if ex.errno == errno.EPIPE:
self.stdin.close()
write_set.remove(self.stdin)
else:
raise
else:
input_offset += bytes_written
if input_offset >= len(input):
self.stdin.close()
write_set.remove(self.stdin)
# Read stdout / stderr by 1024 bytes
for fn, tgt in (
(self.stdout, stdout),
(self.stderr, stderr),
):
if fn in rlist:
data = os.read(fn.fileno(), 1024)
if data == '':
fn.close()
read_set.remove(fn)
tgt.append(data)
if stdout is not None:
stdout = ''.join(stdout)
if stderr is not None:
stderr = ''.join(stderr)
return (stdout, stderr)
这是我的解决方案,我使用线程和事件:
import subprocess
from threading import Thread, Event
def kill_on_timeout(done, timeout, proc):
if not done.wait(timeout):
proc.kill()
def exec_command(command, timeout):
done = Event()
proc = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
watcher = Thread(target=kill_on_timeout, args=(done, timeout, proc))
watcher.daemon = True
watcher.start()
data, stderr = proc.communicate()
done.set()
return data, stderr, proc.returncode
在行动:
In [2]: exec_command(['sleep', '10'], 5)
Out[2]: ('', '', -9)
In [3]: exec_command(['sleep', '10'], 11)
Out[3]: ('', '', 0)