How do you efficiently handle multiple web page requests using PyQt\'s QWebPage without encountering crashes and ensuring proper resource management?

Handling Multiple Web Page Requests in PyQt with QWebPage

When using PyQt's QWebPage to retrieve dynamic content, encountering crashes upon subsequent page load requests can be a common issue. The root cause often lies in improper resource management, leading to memory leaks or object deletion issues. To resolve this, it's crucial to maintain control over the application's event loop and ensure proper resource cleanup.

Solution:

Instead of creating multiple QApplications and instances of QWebPage for each URL, adopt a single QApplication and a single WebPage object. This approach allows for more efficient resource management and avoids the pitfalls of creating and destroying objects repeatedly.

To achieve this, QWebPage's loadFinished signal can be utilized to create an internal event loop within the WebPage object. By connecting a user-defined slot to this signal, custom HTML processing can be performed after each web page is loaded.

Usage:

Here's an example of how to use the WebPage class:

from PyQt4.QtCore import pyqtSignal, QUrl
from PyQt4.QtGui import QApplication
from PyQt4.QtWebKit import QWebPage

class WebPage(QWebPage):
    htmlReady = pyqtSignal(str, str)

    def __init__(self, verbose=False):
        super(WebPage, self).__init__()
        self._verbose = verbose
        self.mainFrame().loadFinished.connect(self.handleLoadFinished)

    def start(self, urls):
        self._urls = iter(urls)
        self.fetchNext()

    def fetchNext(self):
        try:
            url = next(self._urls)
        except StopIteration:
            return False
        else:
            self.mainFrame().load(QUrl(url))
        return True

    def processCurrentPage(self):
        self.htmlReady.emit(
            self.mainFrame().toHtml(), self.mainFrame().url().toString())
        print('loaded: [%d bytes] %s' % (self.bytesReceived(), url))

    def handleLoadFinished(self):
        self.processCurrentPage()
        if not self.fetchNext():
            QApplication.instance().quit()

    def javaScriptConsoleMessage(self, *args, **kwargs):
        if self._verbose:
            super(WebPage, self).javaScriptConsoleMessage(*args, **kwargs)

This approach ensures proper object lifetime management and allows for efficient handling of multiple web page requests within a single PyQt application.

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