FakeRainBrigand FakeRainBrigand - 5 months ago 26
Python Question

How do I make Python, QT, and Webkit work on a headless server?

I have Debian Linux server that I use for a variety of things. I want it to be able to do some web-scraping jobs I need done regularly.

This code can be found here.

import sys
from PyQt4.QtGui import *
from PyQt4.QtCore import *
from PyQt4.QtWebKit import *

class Render(QWebPage):
def __init__(self, url):
self.app = QApplication(sys.argv, False) # Line updated based on mata's answer
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()


A simple test of it would look like this:

url = 'http://example.com'
print Render(url).frame.toHtml()


On the call to the constructor it dies with this message (it's printed to stdout, not an uncaught exception).

: cannot connect to X server


How can I use Python (2.7), QT4, and Webkit on a headless server? Nothing ever needs to be displayed, so I can tweek any settings or anything that need to be tweeked.

I've looked into alternatives, but this is the best fit for me and my projects. If I did have to install an X server, how could I do it with minimal overhead?

Answer

One of the constructors of QApplication takes a boolean argument GUIenabled.
If you use that, you can instantiante QAppliaction without an X server, but you can't create QWidgets.

So in this case the only option is to use a virtual X server like Xvfb to render the GUI.

Xvfb can be installed and run using these commands (assuming you have apt-get installed). The code in the original question is in a file called render.py.

sudo apt-get install xvfb
xvfb-run python render.py