PyQt4：在定时器中调用commands.getoutput()时中断系统调用

Question

这个问题看起来很简单，但我在网上搜索了一整天，包括在StackOverflow上，也没找到解决办法。最开始，我在开发一个简单的plasmoid，它每30分钟会向本地的网络服务器发送一个特定的请求，解析输出并在面板上显示。我参考了一个plasmoid的例子 - BWC-Balance - 然后对它进行了修改。以下是我的代码：

#!/usr/bin/env python
# coding: utf-8

"""
BWC Balance plasmoid

Site: http://bitbucket.org/svartalf/bwc-balance-plasmoid/

Author: SvartalF (http://svartalf.info)
Original idea: m0nochr0me (http://m0nochr0me.blogspot.com)
"""
import re
from urllib import urlencode
import urllib2
import cookielib
import datetime
import sys
import re
import string
import os
import gobject
import commands

from PyQt4.QtCore import *
from PyQt4.QtGui import *
from PyKDE4.kio import *
from PyKDE4.kdeui import *
from PyKDE4.kdecore import *
from PyKDE4.plasma import Plasma
from PyKDE4 import plasmascript
from PyKDE4.solid import Solid

from settings import SettingsDialog

parsed_ok = 0
curr_day = ''

class BWCBalancePlasmoid(plasmascript.Applet):
    """Applet main class"""

    def __init__(self, parent, args=None):
        plasmascript.Applet.__init__(self, parent)

    def init(self):
        """Applet settings"""

        self.setHasConfigurationInterface(True)
        self.setAspectRatioMode(Plasma.Square)

        self.theme = Plasma.Svg(self)
#       self.theme.setImagePath("widgets/background")
#       self.setBackgroundHints(Plasma.Applet.DefaultBackground)

        self.layout = QGraphicsLinearLayout(Qt.Horizontal, self.applet)

        # Main label with balance value
        self.label = Plasma.Label(self.applet)
        self.label.setText(u'<b><font color=blue size=3>No data...</font></b>')

        self.layout.addItem(self.label)
        self.applet.setLayout(self.layout)
        self.resize(350, 30)

        self.startTimer(2500)

    def postInit(self):
        """Start timer and do first data fetching

        Fired only if user opened access to KWallet"""

        self.setLabelText()

    def update(self, value):
        """Update label text"""

        self.label.setText(value)

    def timerEvent(self, event):
        """Create thread by timer"""

        self.setLabelText()
        pass

    def setLabelText(self):
        login = 'mylogin'

        request = 'curl --ntlm -sn http://some.local.resource'

        out_exp = ""
        out_exp = commands.getoutput(request)

        table_name_exp = re.findall(r"some_regular_expression",out_exp)

        tp =  '| html2text | grep -i -A3 ' + login


        out_exp = ''
        try:
            cmd_exp = 'curl --ntlm -sn ' + table_name_exp[0] + ' ' + tp
            out_exp = commands.getoutput(cmd_exp)
        except:
            cmd_exp = ''

        date_check = re.findall(r"one_more_regular_expression", out_exp)

        times_exp  = re.findall(r"[0-9][0-9]:[0-9][0-9]", out_exp )
        if len(times_exp) != 0 and len(date_check) != 0:
            self.label.setText(u'<b><font color=blue size=3>Start: ' + times_exp[0] + u' --- Finish: ' + str(int(string.split(times_exp[0], ':')[0]) + 9) + ':' + string.split(times_exp[0], ':')[1] + ' </span></b>')
        else:
            self.label.setText(u'<b><font color=blue size=3>No data...</span></b>')

def CreateApplet(parent):
    return BWCBalancePlasmoid(parent)

但是我遇到了以下错误：

# plasmoidviewer bwc-balance

plasmoidviewer(25255)/kdecore (services) KServiceFactory::findServiceByDesktopPath: "" not found
plasmoidviewer(25255)/libplasma Plasma::FrameSvg::resizeFrame: Invalid size QSizeF(0, 0) 
plasmoidviewer(25255)/libplasma Plasma::FrameSvg::resizeFrame: Invalid size QSizeF(0, 0) 

Traceback (most recent call last):
  File "/home/grekhov/.kde/share/apps/plasma/plasmoids/bwc-balance/contents/code/main.py", line 116, in timerEvent
    self.setLabelText()
  File "/home/grekhov/.kde/share/apps/plasma/plasmoids/bwc-balance/contents/code/main.py", line 146, in setLabelText
    out_exp = commands.getoutput(request)
  File "/usr/lib/python2.7/commands.py", line 50, in getoutput
    return getstatusoutput(cmd)[1]
  File "/usr/lib/python2.7/commands.py", line 60, in getstatusoutput
    text = pipe.read()
IOError: [Errno 4] Interrupted system call

经过几个小时的搜索，我了解到：从管道读取数据时会被某个信号中断。但我唯一的信号就是定时器。我找到的唯一建议是“摆脱中断你读取的信号”。这对我来说听起来有点奇怪和不现实：定期读取数据而不使用定时器。
我是不是漏掉了什么？也许应该使用其他机制来访问网络资源并解析其输出？或者“中断的系统调用”是正常情况，应该以某种方式处理？

提前感谢你的帮助。

数据解析信号处理网络请求系统调用定时器 pyqt4 plasmoid 中断处理

PyQt4：在定时器中调用commands.getoutput()时中断系统调用

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