下载文件并在python中取消

Question

我正在编写我的 python 脚本以从我的服务器下载一个 xml 文件并将数据并行写入 sqlite3 数据库中。

关于如何使用 urllib2 库从我的服务器取消连接，我需要一些帮助。我希望数据库在连接被取消后立即停止写入数据。 allchannels_timer 将在用户点击“输入”按钮时被调用，该按钮将在连接到我的服务器下载 xml 文件之前等待一秒钟。当我点击退格按钮时，我想停止下载，但目前，代码继续运行，好像什么都没发生一样。

这是我当前的代码：

import urllib2
import StringIO
import sqlite3
import threading
from sqlite3 import dbapi2 as database
from xml.etree import ElementTree
import xml.etree.ElementTree as ET
from UserDict import DictMixin

#get actioncodes from keyboard.xml
ACTION_ENTER = 7
ACTION_BACKSPACE = 110

def cSetVisible(WiNdOw,iD,V=True): WiNdOw.getControl(iD).setVisible(V)

class MyClass(xbmcgui.WindowXML):
     def timer1_8percent(self):
         for i in range(1):
             time.sleep(1)
             self.getControl(4202).setLabel("8%")


     def timer1_12percent(self):
         for i in range(1):
             time.sleep(2)
             self.getControl(4202).setLabel("12%")


     def timer1_18percent(self):
         for i in range(1):
             time.sleep(3)
             self.getControl(4202).setLabel("18%")


     def allchannels_timer(self):
         for i in range(1):
             time.sleep(0.3)
             self.getControl(4202).setLabel("0%")

             #DOWNLOAD THE XML SOURCE HERE
             url = ADDON.getSetting('allchannel.url')
             req = urllib2.Request(url)
             response = urllib2.urlopen(req)
             data = response.read()
             response.close()
             profilePath = xbmc.translatePath(os.path.join('special://userdata/addon_data/script.tvguide', ''))
             self.getControl(4202).setLabel("1%")
             self.thread = threading.Thread(target=self.timer1_8percent)
             self.thread.setDaemon(True)
             self.thread.start()
             self.thread = threading.Thread(target=self.timer1_12percent)
             self.thread.setDaemon(True)
             self.thread.start()
             self.thread = threading.Thread(target=self.timer1_18percent)
             self.thread.setDaemon(True)
             self.thread.start()


             if os.path.exists(profilePath):
                 profilePath = profilePath + 'source.db'
                 con = database.connect(profilePath)
                 cur = con.cursor()
                 cur.execute('CREATE TABLE programs(channel TEXT, title TEXT, start_date TIMESTAMP, stop_date TIMESTAMP, description TEXT)')
                 con.commit()
                 con.close
                 tv_elem = ElementTree.parse(StringIO.StringIO(data)).getroot()
                 profilePath = xbmc.translatePath(os.path.join('special://userdata/addon_data/script.tvguide', ''))
                 profilePath = profilePath + 'source.db'
                 con = sqlite3.connect(profilePath)
                 cur = con.cursor()
                 channels = OrderedDict()

                 # Get the loaded data
                 for channel in tv_elem.findall('channel'):
                     channel_name = channel.find('display-name').text
                     for program in channel.findall('programme'):
                         title = program.find('title').text
                         start_time = program.get("start")
                         stop_time = program.get("stop")
                         cur.execute("INSERT INTO programs(channel, title, start_date, stop_date)" + " VALUES(?, ?, ?, ?)", [channel_name, title, start_time, stop_time])
                         con.commit()
                         con.close

                 print 'Channels store into database are now successfully!'
                 program = None
                 now = datetime.datetime.now()
                 #strCh = '(\'' + '\',\''.join(channelMap.keys()) + '\')'
                 cur.execute('SELECT channel, title, start_date, stop_date FROM programs WHERE channel')
                 getprogram_info = cur.fetchall()

                 for row in getprogram_info:
                     programming = row[0], row[1], row[2], row[3]
                     print programming
                     #print row[0], row[1], row[2], row[3]
                     #programming = row[0], row[1], row[2], row[3]
                     #programming = row[0], row[1], row[2], row[3]
                     #cur.close()


def onAction(self, action):
   img1_yellow = xbmc.getCondVisibility('Control.IsVisible(3)')

   if action == ACTION_BACKSPACE:
     if img1_yellow:
       cSetVisible(self,3,True)
       self.getControl(4202).setLabel("")
       #cancel the connection and close the database


  if action == ACTION_ENTER:
     if img1_yellow:
         cSetVisible(self,3,False)
         self.thread = threading.Thread(target=self.allchannels_timer)
         self.thread.setDaemon(True)
         self.thread.start()

谁能告诉我如何取消与服务器的连接，以便停止下载 xml 文件。我还想知道在取消连接后如何防止数据写入我的数据库。

对于我的问题的任何帮助，我将不胜感激，我们将非常感谢一些示例代码。

Answer 1

要在后台下载文件，同时在前台处理事件，使用Process 会简单得多。他们有更好的 Python 支持，除了 I/O 之外，他们还可以做 CPU，如果他们行动起来就会被杀死。

以下启动后台进程。父母的主循环做自己的事情，不时地检查下载是否完成。如果下载完成，它会继续处理，然后退出。

玩得开心！

来源

import logging, multiprocessing, time, urllib2

def download(url):
    mylog = multiprocessing.get_logger()
    mylog.info('downloading %s', url)
    time.sleep(2)
    req = urllib2.Request(url)
    response = urllib2.urlopen(req)
    data = response.read()
    response.close()
    # more here
    time.sleep(3)
    mylog.info('done')

def main():

    mylog = multiprocessing.log_to_stderr(level=logging.INFO)
    mylog.info('start')

    download_proc = multiprocessing.Process(
        target=download,
        args=('http://example.com',),
        )
    download_proc.start()

    while True:
        mylog.info('ding')
        if download_proc.join(timeout=0.1) is None:
            mylog.info('download done!')
            break
        time.sleep(1)

    mylog.info('done!')

if __name__=='__main__':
    main()

输出

[INFO/MainProcess] start
[INFO/MainProcess] ding
[INFO/Process-1] child process calling self.run()
[INFO/Process-1] downloading http://example.com
[INFO/MainProcess] download done!
[INFO/MainProcess] done!
[INFO/MainProcess] process shutting down
[INFO/MainProcess] calling join() for process Process-1
[INFO/Process-1] done
[INFO/Process-1] process shutting down
[INFO/Process-1] process exiting with exitcode 0