使用PyQt / QtWebkit爬取多个链接
我正在尝试抓取一个大型的政府记录网站，这个过程需要用到一种叫“滚雪球”的方法，也就是说，从主搜索页面开始，然后跟着抓取器找到的每个链接去访问下一个页面。
我已经能够使用PyQt加载主页面，参考了这个SiteScraper教程。
import sys
from PySide.QtGui import *
from PySide.QtCore import *
from PySide.QtWebKit import *
from BeautifulSoup import BeautifulSoup
class Render(QWebPage):
def __init__(self, url):
self.app = QApplication(sys.argv)
QWebPage.__init__(self)
self.loadFinished.connect(self._loadFinished)
self.mainFrame().load(QUrl(url))
self.app.exec_()
def _loadFinished(self, result):
self.frame = self.mainFrame()
self.app.quit()
def main():
baseUrl = 'http://www.thesite.gov'
url = 'http://www.thesite.gov/search'
r = Render(url)
html = r.frame.toHtml()
# use BeautifulSoup to cycle through each regulation
soup = BeautifulSoup(html)
regs = soup.find('div',{'class':'x-grid3-body'}).findAll('a')
# cycle through list and call up each page separately
for reg in regs:
link = baseUrl + reg['href']
link = str(link)
# use Qt to load each regulation page
r = Render(link)
html = r.frame.toHtml() # get actual rendered web page
但是，当我尝试渲染一个新网页时，出现了这个错误：
RuntimeError: A QApplication instance already exists.
我明白这个函数试图调用另一个QApplication实例。但是，我该如何在同一个实例中导航到新页面呢？
class Render(QWebPage):
def __init__(self, app, url):
QWebPage.__init__(self)
self.loadFinished.connect(self._loadFinished)
self.mainFrame().load(QUrl(url))
app.exec_()
def _loadFinished(self, result):
self.frame = self.mainFrame()
def main():
app = QApplication(sys.argv)
baseUrl = 'http://www.thesite.gov'
url = 'http://www.thesite.gov/search'
r = Render(app, url)
html = r.frame.toHtml()
4 个回答
3
你真是疯了！QT的DOM比beautifulsoup好太多了。
把这个：
soup = BeautifulSoup(html)
换成这个：
page = QWebPage()
page.settings().setAttribute(QWebSettings.AutoLoadImages, False)
page.settings().setAttribute(QWebSettings.PluginsEnabled, False)
page.mainFrame().setHtml(html)
dom = page.mainFrame().documentElement()
然后你可以像这样简单地抓取数据：
li = dom.findFirst("body div#content div#special ul > li")
if not li.isNull():
class = li.attribute("class")
text = li.toPlainText()
最后，你应该用QWebView而不是QWebPage。你可以把它设置成像服务器一样，可以通过套接字来控制。这就是我做的：
class QTimerWithPause(QTimer):
def __init__(self, parent = None):
super(QTimerWithPause, self).__init__ (parent)
self.startTime = 0
self.interval = 0
return
def start(self, interval):
from time import time
self.interval = interval
self.startTime = time()
super(QTimerWithPause, self).start(interval)
return
def pause(self):
from time import time
if self.isActive ():
self.stop()
elapsedTime = self.startTime - time()
self.startTime -= elapsedTime
# time() returns float secs, interval is int msec
self.interval -= int(elapsedTime*1000)+1
return
def resume(self):
if not self.isActive():
self.start(self.interval)
return
class CrawlerWebServer(QWebView):
TIMEOUT = 60
STUPID = r"(bing|yahoo|google)"
def __init__(self, host="0.0.0.0", port=50007, parent=None, enableImages=True, enablePlugins=True):
# Constructor
super(CrawlerWebServer, self).__init__(parent)
self.command = None
self.isLoading = True
self.isConnected = False
self.url = QUrl("http://mast3rpee.tk/")
self.timeout = QTimerWithPause(self)
self.socket = QTcpServer(self)
# 1: Settings
self.settings().enablePersistentStorage()
self.settings().setAttribute(QWebSettings.AutoLoadImages, enableImages)
self.settings().setAttribute(QWebSettings.PluginsEnabled, enablePlugins)
self.settings().setAttribute(QWebSettings.DeveloperExtrasEnabled, True)
# 2: Server
if args.verbosity > 0: print "Starting server..."
self.socket.setProxy(QNetworkProxy(QNetworkProxy.NoProxy))
self.socket.listen(QHostAddress(host), int(port))
self.connect(self.socket, SIGNAL("newConnection()"), self._connect)
if args.verbosity > 1:
print " Waiting for connection(" + host + ":" + str(port) + ")..."
# 3: Default page
self._load(10*1000, self._loadFinished)
return
def __del__(self):
try:
self.conn.close()
self.socket.close()
except:
pass
return
def _sendAuth(self):
self.conn.write("Welcome to WebCrawler server (http://mast3rpee.tk)\r\n\rLicenced under GPL\r\n\r\n")
def _connect(self):
self.disconnect(self.socket, SIGNAL("newConnection()"), self._connect)
self.conn = self.socket.nextPendingConnection()
self.conn.nextBlockSize = 0
self.connect(self.conn, SIGNAL("readyRead()"), self.io)
self.connect(self.conn, SIGNAL("disconnected()"), self.close)
self.connect(self.conn, SIGNAL("error()"), self.close)
self._sendAuth()
if args.verbosity > 1:
print " Connection by:", self.conn.peerAddress().toString()
self.isConnected = True
if self.isLoading == False:
self.conn.write("\r\nEnter command:")
return
def io(self):
if self.isLoading: return None
if args.verbosity > 0:
print "Reading command..."
data = self.conn.read(1024).strip(" \r\n\t")
if not data: return None
elif self.command is not None:
r = self.command(data)
self.command = None
return r
return self._getCommand(data)
def _getCommand(self, d):
from re import search
d = unicode(d, errors="ignore")
if search(r"(help|HELP)", d) is not None:
self.conn.write("URL | JS | WAIT | QUIT\r\n\r\nEnter Command:")
elif search(r"(url|URL)", d) is not None:
self.command = self._print
self.conn.write("Enter address:")
elif search(r"(js|JS|javascript|JAVASCRIPT)", d) is not None:
self.command = self._js
self.conn.write("Enter javascript to execte:")
elif search(r"(wait|WAIT)", d) is not None:
self.loadFinished.connect(self._loadFinishedPrint)
self.loadFinished.connect(self._loadFinished)
elif search(r"(quit|QUIT|exit|EXIT)", d) is not None:
self.close()
else:
self.conn.write("Invalid command!\r\n\r\nEnter Command:")
return
def _print(self, d):
u = d[:250]
self.out(u)
return True
def _js(self, d):
try:
self.page().mainFrame().evaluateJavaScript(d)
except:
pass
self.conn.write("Enter Javascript:")
return True
def _stop(self):
from time import sleep
if self.isLoading == False: return
if args.verbosity > 0:
print " Stopping..."
self.timeout.stop()
self.stop()
def _load(self, timeout, after):
# Loads a page into frame / sets up timeout
self.timeout.timeout.connect(self._stop)
self.timeout.start(timeout)
self.loadFinished.connect(after)
self.load(self.url)
return
def _loadDone(self, disconnect = None):
from re import search
from time import sleep
self.timeout.timeout.disconnect(self._stop)
self.timeout.stop()
if disconnect is not None:
self.loadFinished.disconnect(disconnect)
# Stick a while on the page
if search(CrawlerWebServer.STUPID, self.url.toString(QUrl.RemovePath)) is not None:
sleep(5)
else:
sleep(1)
return
def _loadError(self):
from time import sleep, time
if not self.timeout.isActive(): return True
if args.verbosity > 0: print " Error retrying..."
# 1: Pause timeout
self.timeout.pause()
# 2: Check for internet connection
while self.page().networkAccessManager().networkAccessible() == QNetworkAccessManager.NotAccessible: sleep(1)
# 3: Wait then try again
sleep(2)
self.reload()
self.timeout.resume()
return False
def go(self, url, after = None):
# Go to a specific address
global args
if after is None:
after = self._loadFinished
if args.verbosity > 0:
print "Loading url..."
self.url = QUrl(url)
self.isLoading = True
if args.verbosity > 1:
print " ", self.url.toString()
self._load(CrawlerWebServer.TIMEOUT * 1000, after)
return
def out(self, url):
# Print html of a a specific url
self.go(url, self._loadFinishedPrint)
return
def createWindow(self, windowType):
# Load links in the same web-view.
return self
def _loadFinished(self, ok):
# Default LoadFinished
from time import sleep
from re import search
if self.isLoading == False: return
if ok == False:
if not self._loadError(): return
self._loadDone(self._loadFinished)
if args.verbosity > 1:
print " Done"
if self.isConnected == True:
self.conn.write("\r\nEnter command:")
self.isLoading = False
return
def _loadFinishedPrint(self, ok):
# Print the evaluated HTML to stdout
if self.isLoading == False: return
if ok == False:
if not self._loadError(): return
self._loadDone(self._loadFinishedPrint)
if args.verbosity > 1:
print " Done"
h = unicode( self.page().mainFrame().toHtml(), errors="ignore" )
if args.verbosity > 2:
print "------------------\n" + h + "\n--------------------"
self.conn.write(h)
self.conn.write("\r\nEnter command:")
self.isLoading = False
return
def contextMenuEvent(self, event):
# Context Menu
menu = self.page().createStandardContextMenu()
menu.addSeparator()
action = menu.addAction('ReLoad')
@action.triggered.connect
def refresh():
self.load(self.url)
menu.exec_(QCursor.pos())
class CrawlerWebClient(object):
def __init__(self, host, port):
import socket
global args
# CONNECT TO SERVER
self.socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
self.socket.connect((host, port))
o = self.read()
if args.verbosity > 2:
print "\n------------------------------\n" + o + "\n------------------------------\n"
return
def __del__(self):
try: self.socket.close()
except: pass
def read(self):
from re import search
r = ""
while True:
out = self.socket.recv(64*1024).strip("\r\n")
if out.startswith(r"Enter"):
break
if out.endswith(r"Enter command:"):
r += out[:-14]
break
r += out
return r
def command(self, command):
global args
if args.verbosity > 2:
print " Command: [" + command + "]\n------------------------------"
self.socket.sendall(unicode(command))
r = self.read()
if args.verbosity > 2:
print r, "\n------------------------------\n"
return r
6
我也遇到过同样的问题（需要用QWebPage加载多个页面），但是我试了这些答案都没用。这里有一个有效的方法，关键是使用QEventLoop，并把loadFinished连接到loop.quit上：
from PySide import QtCore, QtGui, QtWebKit
import sys
def loadPage(url):
page = QtWebKit.QWebPage()
loop = QtCore.QEventLoop() # Create event loop
page.mainFrame().loadFinished.connect(loop.quit) # Connect loadFinished to loop quit
page.mainFrame().load(url)
loop.exec_() # Run event loop, it will end on loadFinished
return page.mainFrame().toHtml()
app = QtGui.QApplication(sys.argv)
urls = ['https://google.com', 'http://reddit.com', 'http://wikipedia.org']
for url in urls:
print '-----------------------------------------------------'
print 'Loading ' + url
html = loadPage(url)
print html
app.exit()
这里发一个简化的例子，比起原问题的例子更简单，目的是为了展示核心问题和解决方案。
2
好的，如果你真的需要用JavaScript的话。（你能从JSON中获取答案吗？那样可能会更简单，使用simplejson或json就可以了。）答案是不要创建多个QApplication。这是不允许的。让main去创建一个QApplication，然后直接使用QWebPage，不用去调用QApplication.exec_()。如果这样不行，就把所有的内容放在另一个QThread里运行。