陷入 While True 循环……关于如何退出的任何想法？

Question

编辑 #1：这是工作代码，但有时我会收到一个 UnicodeDecodeError，它会停止循环继续。无论如何，发生这种情况时是否会导致循环中断或通过？我尝试将代码更改为 Try 而不是 If 语句，但它不起作用...

我的问题是在 while True: statement...

def SerialRead(dataReadEvent):
    delay1 = DT.datetime.now()                
    dataReadEvent.set()


    #Serial Reading    
    ser = serial.Serial(port='COM4', baudrate=9600, bytesize=serial.EIGHTBITS, parity=serial.PARITY_NONE, stopbits=serial.STOPBITS_ONE, timeout=None)   

    global last_received
    buffer = ''
    amountAppended = 0
    while True:
        buffer += ser.read(ser.inWaiting()).decode('ascii')
        if '\n' in buffer:
            last_received, buffer = buffer.split('\n')[-2:] 
            amountAppended += 1
        if amountAppended == 2:
            amountAppended =0
            break      
    else:
        ser.close()

    global plaintext1
    plaintext1 = last_received.replace(' ', ', ')    
    plaintext = plaintext1.replace('=', ', ')
    global listvalue
    listvalue = plaintext.split(", ")

    #Writing to csv
    outputfile = open(location, mode='a', newline='')
    outputWriter = csv.writer(outputfile)
    outputWriter.writerow([plaintext])
    outputfile.close()     

    delay2 = DT.datetime.now()
    differencetime = (delay2 - delay1).total_seconds()
    restart = (writedelay - differencetime)
    threading.Timer(restart, SerialRead, args=(dataReadEvent,)).start()

我试图让我的串行连接每 5 秒读取最后一行输入。但是，我在线程命令中植入了一个 While True 循环，我无法退出 While True 循环......它总是在它参与时。

While True 循环允许我从我的设备中获取一整行串行数据。我需要一条完整的正确路线，这就是做到这一点的方法，但每次都会遇到麻烦。我怎样才能摆脱循环？

from PyQt4 import QtGui, QtCore
import sys
import masimo
import csv
import time
import datetime as DT
import threading
from threading import Thread
import serial
import os

os.chdir(r"C:\Users\SpO2\Desktop\Data")
time1 = time.strftime("%d %b %Y %H%M%S")
location = r'%s.csv' % time1
outputfile = open(location, mode='x', newline='')
outputWriter = csv.writer(outputfile)
outputWriter.writerow(["start"])
outputfile.close()
writedelay = int(5)
last_received = ''

class ExampleApp(QtGui.QMainWindow, masimo.Ui_MainWindow):            
    def __init__(self, event, parent=None):
        super(self.__class__, self).__init__()
        self.setupUi(self)

        self.dataWasReadEvent = event
        self.checkThreadTimer = QtCore.QTimer(self)
        self.checkThreadTimer.setInterval(500) #.5 seconds
        self.checkThreadTimer.timeout.connect(self.readListValues) 
        self.checkThreadTimer.start()

    def readListValues(self):
        if self.dataWasReadEvent.is_set():
                #Read your events from the list and update your fields
            self.SPO2text.setText(str(listvalue[5]))
            self.HRtext.setText(str(listvalue[7]))
            self.PItext.setText(str(listvalue[9]))
            self.timestamptext.setText(str(listvalue[1]))
            self.rawdata.setText(str(plaintext1))
            self.dataWasReadEvent.clear() #Clear the event set flag so that nothing happens the next time the timer times out

def SerialRead(dataReadEvent):
    delay1 = DT.datetime.now()                
    dataReadEvent.set()


    #Serial Reading    
    ser = serial.Serial(port='COM4', baudrate=9600, bytesize=serial.EIGHTBITS, parity=serial.PARITY_NONE, stopbits=serial.STOPBITS_ONE, timeout=2)   

    global last_received
    buffer = ''
    while True:
        buffer += ser.read(ser.inWaiting()).decode('ascii')
        if '\n' in buffer:
            last_received, buffer = buffer.split('\n')[-2:] 
    else:
        ser.close()



    global plaintext1
    plaintext1 = last_received.replace(' ', ', ')    
    plaintext = plaintext1.replace('=', ', ')
    global listvalue
    listvalue = plaintext.split(", ")

    #Writing to csv
    outputfile = open(location, mode='a', newline='')
    outputWriter = csv.writer(outputfile)
    outputWriter.writerow([plaintext])
    outputfile.close()     

    delay2 = DT.datetime.now()
    differencetime = (delay2 - delay1).total_seconds()
    restart = (writedelay - differencetime)
    threading.Timer(restart, SerialRead, args=(dataReadEvent,)).start()    

def main(dataReadEvent):
    app = QtGui.QApplication(sys.argv)
    form = ExampleApp(dataReadEvent)
    form.show()
    sys.exit(app.exec_())


if __name__ == '__main__':
    dataReadEvent = threading.Event()
    Thread(target = SerialRead, args=(dataReadEvent,) ).start()
    Thread(target = main, args=(dataReadEvent,) ).start()

Answer 1

使用break关键字退出任何循环。它将退出 break 所在的任何循环。

Answer 2

您的循环开始于

 while True:

这将永远持续下去查看这两个示例并注意差异

a=0 
while a<10:
   print a
   a = a+1

这将打印 0 1 2 3 4 ... 9，然后 a 递增到 10。表达式的计算结果为 false，循环退出。

现在：

a=1
while a>0:
   print a 
   a = a+1

这将运行永远，因为 a 总是大于 0

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然后使用last_recieved中的两行作为测试。

while last_received_count <2:
  .... 
  ....
    if '\n' in buffer:
       last_received, buffer = buffer.split('\n')[-2:]
       last_received_count = last_received_count+1

Answer 3

while True:

函数永远不会结束也不会退出，可以用"break"退出循环。如果这不是您想要的，您必须告诉它 while 语句何时应该处于活动状态，即：

While amountOfTimesToLoop < 0: do whatever

如果你想检查什么时候添加到你的列表中，你可以这样做

while True:
    buffer += ser.read(ser.inWaiting()).decode('ascii')
    if '\n' in buffer:
        last_received, buffer = buffer.split('\n')[-2:] 
    if last_received.length == 2:
        break
else:
    ser.close()

或者，如果您不清除列表，您可以使用

amountAppended = 0
while True:
    buffer += ser.read(ser.inWaiting()).decode('ascii')
    if '\n' in buffer:
        last_received, buffer = buffer.split('\n')[-2:] 
        amountAppended += 1
    if amountAppended == 2:
        amountAppended = 0
        break
else:
    ser.close()

Answer 4

如您所愿 "run the loop until i have two lines of data appended to 'last_received'"，您可以使用 counter，它在 if 语句内递增，然后 break 当 counter 值为等于 2。像这样：

counter = 1
while True:
   buffer += ser.read(ser.inWaiting()).decode('ascii')
       if '\n' in buffer:
           last_received, buffer = buffer.split('\n')[-2:] 
           if counter == 2:
               break
           counter += 1

陷入 While True 循环……关于如何退出的任何想法？

Stuck in a While True loop... any ideas on how to get out?

python

multithreading

serial-port

while-loop

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