python - 如何在类中使用 Python 中的多重处理

Question

我想做的是在我的类方法之一上使用多重处理。我尝试按照 Python 帮助文件中的示例进行操作，但没有得到预期的结果。这是我的类文件:

import os
import telnetlib

class PowerSupply():

    # ---------------------------------- #
    def __init__(self,port_no,my_name):
        self.Status = "Off"
        self.Port = port_no
        self.Name = my_name
        self.tn = None
        self.HOST = "192"
        self.P = Process(target=self.print_time, args=('tname','delay')
        self.P.start()
        self.P.join()
    # ---------------------------------- #
    def TurnOn(self):
        onCommand = "OUT 1\r"

        if self.Status == "ON":
            print "I'm already on"
        else:
            self.tn = telnetlib.Telnet(self.HOST,self.Port)
            self.tn.write(onCommand)
            self.Status = "ON"
            print "I am now on"
    # ---------------------------------- #
    def TurnOff(self):
        offCommand = "OUT 0\r"
        self.tn.write(offCommand)
        self.tn.close()
        print "I am now off"
    # ---------------------------------- #
    def SetVoltage(self,volts):
        voltageCommand = "PV" + " " + str(volts) + "\r"
        self.tn.write(voltageCommand)
    # ---------------------------------- #  
    def GetAllData(self):
        while(self.Status == "ON"):
            self.tn.write("DVC?\r")
            all_data = self.tn.read_some()
            vdc = all_data.split(',')
            vdc = vdc[0]
            print vdc
    # ---------------------------------- #
    def print_time(self, tname, delay):
       count = 0
       while count < 5:
        time.sleep(delay)
        count += 1
        print "%s: %s"%(tname, time.ctime(time.time()))

以下是我尝试使用该实现的方法:

ps1 = PowerSuppy(8000,'L1')
ps1.print_time('thread1',2)
ps1.print_time('thread2',3)

当我尝试像上面那样使用它时，它仍然使用过程方法，并且在线程 1 完成之前不会调用线程 2。我到底做错了什么以及如何解决它？

Answer 1

好的，我认为该程序将执行以下操作:

1. 在 PowerSuppy(8000,'L1') 处，它启动一个子进程并调用 self.print_time('tname','delay')。由于 'delay' 不是一个数字，它会立即在子进程中引发 TypeError 并结束(因此 self.P.join() 没有'根本不阻止)。
2. 在 ps1.print_time('thread1',2) 处，它运行主进程中的方法，并被阻塞直至结束。
3. ps1.print_time('thread2',3) 与上一行在主进程中执行的操作相同。

如何解决:

1. 不要在__init__方法中初始化子进程，而是在print_time方法中初始化它。
2. 为子流程的target函数实现了内部方法。
3. 除非您想按顺序运行子流程，否则请勿运行 Process.join。

代码如下:

import os
import telnetlib

class PowerSupply():

    # ---------------------------------- #
    def __init__(self,port_no,my_name):
        self.Status = "Off"
        self.Port = port_no
        self.Name = my_name
        self.tn = None
        self.HOST = "192"

    # ---------------------------------- #
    def TurnOn(self):
        onCommand = "OUT 1\r"

        if self.Status == "ON":
            print "I'm already on"
        else:
            self.tn = telnetlib.Telnet(self.HOST,self.Port)
            self.tn.write(onCommand)
            self.Status = "ON"
            print "I am now on"
    # ---------------------------------- #
    def TurnOff(self):
        offCommand = "OUT 0\r"
        self.tn.write(offCommand)
        self.tn.close()
        print "I am now off"
    # ---------------------------------- #
    def SetVoltage(self,volts):
        voltageCommand = "PV" + " " + str(volts) + "\r"
        self.tn.write(voltageCommand)
    # ---------------------------------- #  
    def GetAllData(self):
        while(self.Status == "ON"):
            self.tn.write("DVC?\r")
            all_data = self.tn.read_some()
            vdc = all_data.split(',')
            vdc = vdc[0]
            print vdc
    # ---------------------------------- #
    def print_time(self, tname, delay):
        P = Process(target=self._print_time, args=(tname, delay))
        P.start()

    def _print_time(tname, delay):
        count = 0
        while count < 5:
            time.sleep(delay)
        count += 1
        print "%s: %s"%(tname, time.ctime(time.time()))