How to Safely Scrape Multiple URLs with QWebPage in Qt without Crashing?

Scrape Multiple URLs with QWebPage: Prevent Crashes

In Qt, using QWebPage to retrieve dynamic web content can be problematic when scraping multiple pages consecutively. The following issue highlights potential crash scenarios:

Issue:

Using QWebPage to render a second page often results in crashes. Sporadic crashing or segfaults occur when the object used for rendering is not deleted properly, leading to potential problems upon reuse.

QWebPage Class Overview:

The QWebPage class offers methods for loading and rendering web pages. It emits a loadFinished signal when the loading process is complete.

Solution:

To address the crashing issue, it's recommended to create a single QApplication and WebPage instance and utilize the WebPage's loadFinished signal to fetch and process URLs continuously.

PyQt5 WebPage Example:

<code class="python">import sys

class WebPage(QWebEnginePage):

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

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

    def fetchNext(self):
        try:
            url = next(self._urls)
        except StopIteration:
            MyApp.instance().quit()  # Close app instead of crashing
        else:
            self.load(QUrl(url))

    def processCurrentPage(self, html):
        # Custom HTML processing goes here
        print('Loaded:', str(html), self.url().toString())

    def handleLoadFinished(self):
        self.toHtml(self.processCurrentPage)</code>

Usage:

<code class="python">import sys

app = QApplication(sys.argv)
webpage = WebPage(verbose=False)

# Example URLs to process
urls = ['https://example.com/page1', 'https://example.com/page2', ...]

webpage.process(urls)

sys.exit(app.exec_())</code>

This approach ensures that the QWebPage object is properly managed and avoids crashes by controlling the fetching and processing of URLs within a single event loop.

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