Here's the patch:

--- pywikipedia/xmlreader.py    2010-03-26 22:45:58.000000000 -0700
+++ xmlreader.py    2010-04-08 23:35:51.000000000 -0700
@@ -285,6 +285,9 @@
         if self.filename.endswith('.bz2'):
             import bz2
             source = bz2.BZ2File(self.filename)
+        if self.filename.endswith('.7z'):
+            import subprocess
+            source = subprocess.Popen('7za e -bd -so %s 2>/dev/null' % self.filename, shell=True, stdout=subprocess.PIPE, bufsize=65535).stdout
         else:
             # assume it's an uncompressed XML file
             source = open(self.filename)

-- Dc987