PyQt image capturing error

Question

I am trying to go to set of url and capture there snapshots using PyQt, the code works fine for one url :

#!/usr/bin/env python
import sys, itertools
import signal
from PyQt4.QtCore import *
from PyQt4.QtGui import *
from PyQt4.QtWebKit import QWebPage

urls = "http://www.gouvernement.fr/", "http://www.google.com/"
outputs = "output1.png", "output2.png"
 #for url in urls: #and output in ouputs:
for url, output in itertools.izip(urls, outputs):

    def onLoadFinished(result):
    if not result:
        print "Request failed"
        sys.exit(1)

    # Set the size of the (virtual) browser window
    webpage.setViewportSize(webpage.mainFrame().contentsSize())

    # Paint this frame into an image
    image = QImage(webpage.viewportSize(), QImage.Format_ARGB32)
    painter = QPainter(image)
    webpage.mainFrame().render(painter)
    painter.end()
    image.save(output)
    print ".png image successfully saved"
    #sys.exit(0)


    app = QApplication(sys.argv)
    signal.signal(signal.SIGINT, signal.SIG_DFL)

    webpage = QWebPage()
    webpage.connect(webpage, SIGNAL("loadFinished(bool)"), onLoadFinished)
    webpage.mainFrame().load(QUrl(url))
    sys.exit(app.exec_())

But as it goes throuhg one snapshot it just hangs and doesnt go on for the next snapshot. Why is that ?

Answer 1

The indenting of the code you pasted doesn't make it clear how far your for loop goes - I presume everyting until the end is within the loop?

If so, then it's clear why your code doesn't work: you call app.exec_, which will block until the last window is closed or you call quit or exit. As you never do, it blocks forever.

If you want to process multiple urls this way, you should use your event handlers to save the page and load the next url. Something like this should work:

#!/usr/bin/env python
import sys, itertools
import signal
from PyQt4.QtCore import *
from PyQt4.QtGui import *
from PyQt4.QtWebKit import QWebPage

urls = ["http://www.gouvernement.fr/", "http://www.google.com/"]
outputs = ["output1.png", "output2.png"]

def save_page(webpage, output):
    # Set the size of the (virtual) browser window
    webpage.setViewportSize(webpage.mainFrame().contentsSize())

    # Paint this frame into an image
    image = QImage(webpage.viewportSize(), QImage.Format_ARGB32)
    painter = QPainter(image)
    webpage.mainFrame().render(painter)
    painter.end()
    image.save(output)
    print ".png image successfully saved"
    #sys.exit(0)


app = QApplication(sys.argv)
signal.signal(signal.SIGINT, signal.SIG_DFL)

webpage = QWebPage()

def onLoadFinished(result):
    if not result:
        print "Request failed"
        sys.exit(1)
    save_page(webpage, outputs.pop(0))   # pop output name from list and save
    if urls:
        url = urls.pop(0)   # pop next url to fetch from list
        webpage.mainFrame().load(QUrl(url))
    else:
        app.quit()  # exit after last url

webpage.connect(webpage, SIGNAL("loadFinished(bool)"), onLoadFinished)
webpage.mainFrame().load(QUrl(urls.pop(0)))
sys.exit(app.exec_())