Python - 子流程 - 记录和转储测量

Question

在带有 Ubuntu 16.04LTS 的 python3 中，我有一个从主脚本创建的子进程，用于记录连接到本地机器的设备的测量值。我想知道如何在我想完成数据记录时向此子过程发送消息，并切换到将测量结果转储到 csv 文件。下面显示的是我到目前为止尝试过的精简版本，但代码挂起，我无法转储我记录的测量值。事实上，我只记录了 1 次测量。我不确定如何在记录数据时异步检查 stdin 输入。我可以得到一些帮助吗？

Main.py

# start subprocess
p_1 = subprocess.Popen(["./ekg.py", saveFilename_ekg], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
# do other stuff
...
# send message to quit
message = str("1")
encMsg = message.encode()
print("Message:", encMsg.decode())
p_stdout = p_1.communicate(input=encMsg)[0]
# print "Done" from subprocess 
print(p_stdout.decode('utf-8').strip())
# kill subprocess
p_1.kill()

ekg.py

def dumpLiveData(outputFile):
ekg = ekgClass()
dataMeasurements = []
for liveData in ekg.getLiveData():
# monitor stdin for message
if int(sys.stdin.read()) == 1:
break
else:
meas = [liveData.time, liveData.pulseWaveform]
dataMeasurements.append(meas)
#print ("Dumping data")
with open(outputFile, 'wb') as csvfile:
writer = csv.writer(csvfile, quoting=csv.QUOTE_NONNUMERIC)
#print ("Created text file")
header = ["Time", "Waveform value"]
writer.writerow(header)
for idx, val in enumerate(dataMeasurements):
writer.writerow(dataMeasurements[idx])    
print("Done")

if __name__== "__main__":  
# get parameters
parser = argparse.ArgumentParser(description="ekg.py")
parser.add_argument("outputFile", help="Output CSV file.")
# parse
args = parser.parse_args()
# record and dump measurements
dumpLiveData(args.outputFile)

Answer 1

通过向子进程发送控件 + C 事件来解决它。一个 try-except-else 块捕获了键盘中断，对其进行了处理，然后我优雅地退出了该块。退出后，我将记录的数据写入csv文件。

main.py

import subprocess, signal 
# start subprocess
p_1 = subprocess.Popen(["./ekg.py", saveFilename_ekg], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
# do other stuff
...
# send control + C event
p_1.send_signal(signal.SIGINT)
stdout, stderr = p_1.communicate(input=encMsg)[0]
# print output from subprocess 
print(stdout.decode('utf-8').strip())
# wait for subprocess to write file
p_1.wait()
# kill subprocess
p_1.kill()

ekg.py

def dumpLiveData(outputFile):
ekg = ekgClass()
dataMeasurements = []
exception_found = None
try:
for liveData in ekg.getLiveData():
if exception_found == True:
break
meas = [liveData.time, liveData.pulseWaveform]
dataMeasurements.append(meas)
except KeyboardInterrupt:
exception_found = True
else:
pass
print ("Dumping data")
with open(outputFile, 'wb') as csvfile:
writer = csv.writer(csvfile, quoting=csv.QUOTE_NONNUMERIC)
print ("Created text file")
header = ["Time", "Waveform value"]
writer.writerow(header)
for idx, val in enumerate(dataMeasurements):
writer.writerow(dataMeasurements[idx])    
print("Done")