Clash Royale CLAN TAG

subprocess sometimes sends returns empty

I have the following class that is used to run a third party command line tool which I have no control over.

I run this ina Qthread in a PyQt Gui.

Qthread

PyQt

I turn the gui into an EXE using Pyinstaller

gui

EXE

Pyinstaller

Problems are more prevalent when it is an EXE

EXE

class CLI_Interface:

def process_f(self, command, bsize=4096):

self.kill_process(CLI_TOOL)

startupinfo = STARTUPINFO()
startupinfo.dwFlags |= STARTF_USESHOWWINDOW
startupinfo.wShowWindow = SW_HIDE

p = Popen(command, stdout=PIPE, stderr=PIPE,
startupinfo=startupinfo, bufsize=bsize, universal_newlines=True)
try:
out, err = p.communicate(timeout=120)
except TimeoutExpired:
p.kill()
out, err = p.communicate()
return out.split(), err.split()


def kill_process(self, proc):
# Check process is running, Kill it if it is,
# return False if not.
# uses its own popen for Stderr >> stdout
# If we use the self.process_f method, it will create an infinite loop

startupinfo = STARTUPINFO()
startupinfo.dwFlags |= STARTF_USESHOWWINDOW
startupinfo.wShowWindow = SW_HIDE
try:
kill_proc = Popen("TaskKill /IM {} /T /F".format(proc), stdout=PIPE, stderr=STDOUT,
startupinfo=startupinfo, universal_newlines=True).communicate()[0]
if 'ERROR' not in kill_proc.split():
return True # Process Killed
else:
self.kill_process(proc)
except Exception as e:
return False


def download_data(self, code):
""" download data from the device based on a 5 digit code """

command = '"{}" -l {},{} {}'.format(CLI_TOOL_PATH,
code[0], code[2], code[1])
try:
p = self.process_f(command)
proc, err = p[0], p[1]
try:
if err[-2] == '-p':
return False
return True
except IndexError:
if not proc:
return False
pass
return True
except Exception as e:
return False

def ....
def ....
def ....


Thread:

class GetDataThread(QThread):

taskFinished = pyqtSignal()
notConnected = pyqtSignal()

def __init__(self, f, parent=None):
super(GetDataThread, self).__init__(parent)
self.f = f

def run(self):

is_dongle_connected()

DD = cli.download_data(self.f)

if not DD:
self.notConnected.emit()
else:
self.taskFinished.emit()


I either get a done! or error - This is normal when running from the command line.

done!

error

Sometimes I get an empty list returned and I put this back into a recursive loop after killing the program.

empty list

However, it does not seem to restart properly and the problem continues - it gets stuck in a loop of nothing!.

Meanwhile, the csv files the cli tool produces are created as normal yet I have no data from stdout / stderr

stdout / stderr

Looking at processes the conhost and the cli tool are destroyed no problem.

conhost

cli

The gui will continue to fail (until I unplug and plug in the dongle and / or restart the program / computer.

When I open the CLI and run the same command, it works fine or throws an error (which I catch in the program no problem)

I have tried setting a buffer as some files generated can reach 2.4mb

2.4mb

I tried setting a higher timeout to allow for it to finish.

There does not seem to be a correlation with file size though and it can get stuck at any size.

The flow is like so:

Gui >> CLI >> Dongle >> Sensor

Running on Windows 10

How can I make the connection more solid or debug what processes might still be lingering around and stopping this?

Is it blocking?

Is it a pipe buffer overflow? - If so How do I determine the correct bufsize?

bufsize

Is it something to do with PyQt and Python Subprocess or Pyinstaller?

Would it be better to use QProcess instead of Subprocess?

QProcess

Subprocess

Thanks in advance!

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