Windows上的Python 2.6：如何使用“shell = True”参数终止subpr

import wx
import threading
import subprocess

class MainWindow(wx.Frame):

    def __init__(self,parent,id,title):        
        wx.Frame.__init__(self,title)
        self.main_panel = wx.Panel(self,-1)

        self.border_sizer = wx.BoxSizer()

        self.process_button = wx.Button(self.main_panel,-1,"Start process",(50,50))
        self.process_button.Bind(wx.EVT_BUTTON,self.processButtonClick)

        self.border_sizer.Add(self.process_button)
        self.main_panel.SetSizerAndFit(self.border_sizer)
        self.Fit()

        self.Centre()
        self.Show(True)

    def processButtonClick(self,event):
        if self.process_button.GetLabel() == "Start process":
            self.process_button.SetLabel("End process")
            self.notepad = threading.Thread(target = self.runProcess)
            self.notepad.start()
        else:
            self.cancel = 1
            self.process_button.SetLabel("Start process")

    def runProcess(self):
        self.cancel = 0

        notepad_process = subprocess.Popen("notepad",shell = False)

        while notepad_process.poll() == None: # While process has not yet terminated.
            if self.cancel:
                notepad_process.terminate()
                break

def main():
    app = wx.PySimpleApp()
    mainView = MainWindow(None,wx.ID_ANY,"test")
    app.MainLoop()

if __name__ == "__main__":
    main()

请接受这个问题,“shell”必须等于“True”.