PyQt QFileDialog - Multiple Directory Selection

I am trying to create a QFileDialog that allows the user to select multiple directories.

Following the discussion here and the faq here, but I'm not sure what I'm doing wrong. I get a file dialog, but it still only lets me select a single directory (folder).

This is on Windows 7

Code:

class FileDialog(QtGui.QFileDialog):
        def __init__(self, *args):
            QtGui.QFileDialog.__init__(self, *args)
            self.setOption(self.DontUseNativeDialog, True)
            self.setFileMode(self.DirectoryOnly)

            self.tree = self.findChild(QtGui.QTreeView)
            self.tree.setSelectionMode(QtGui.QAbstractItemView.MultiSelection)

            self.list = self.findChild(QtGui.QListView)
            self.list.setSelectionMode(QtGui.QAbstractItemView.MultiSelection)

if __name__ == '__main__':
    import sys
    app = QtGui.QApplication(sys.argv)
    ex = FileDialog()
    ex.show()
    sys.exit(app.exec_())

Edit:

So after playing around with this some more, if I select "Detail View" in the file dialog, multiselection works. However, if I select "List View" it does not work. Any idea why?

The example code from the FAQ is not robust, because it assumes the dialog only has one QListView and one QTreeView. The behaviour of findChild is indeterminate when there are several direct child objects: so it was probably just pure luck that it ever worked.

A more robust solution would be to reset the selection mode on any view for which the type of its model is a QFileSystemModel:

for view in self.findChildren((QtGui.QListView, QtGui.QTreeView)):
    if isinstance(view.model(), QtGui.QFileSystemModel):
        view.setSelectionMode(QtGui.QAbstractItemView.MultiSelection)