[PyQt] newly introduced bug in PyQt 4.8.1 uic.loadUi

Paul Du Bois dubois at doublefine.com
Mon Dec 6 01:24:06 GMT 2010

This change to PyQt4/uic/Loader/loader.py loadUi() breaks support for
file-like objects,
but uic.loadUi() is still documented as supporting them:

        # Allow the filename to be a QString.
        filename = str(filename)

        return self.parse(filename, os.path.dirname(filename))

The use case for file-like objects is wrapping up apps via py2exe or

Here is an example of the problem:

>>> from PyQt4 import uic
>>> help(uic.loadUi)
Help on function loadUi in module PyQt4.uic:

loadUi(uifile, baseinstance=None)
    loadUi(uifile, baseinstance=None) -> widget

    Load a Qt Designer .ui file and return an instance of the user

    uifile is a file name or file-like object containing the .ui file.
    baseinstance is an optional instance of the Qt base class.  If
    then the user interface is created in it.  Otherwise a new instance
of the
    base class is automatically created.

>>> import StringIO
>>> f = StringIO.StringIO("foo")
>>> uic.loadUi(f)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\python26\lib\site-packages\PyQt4\uic\__init__.py", line 185,
in loadUi
    return DynamicUILoader().loadUi(uifile, baseinstance)
  File "C:\python26\lib\site-packages\PyQt4\uic\Loader\loader.py", line
31, in loadUi
    return self.parse(filename, os.path.dirname(filename))
  File "C:\python26\lib\site-packages\PyQt4\uic\uiparser.py", line 817,
in parse
    document = parse(filename)
  File "C:\python26\lib\xml\etree\ElementTree.py", line 862, in parse
    tree.parse(source, parser)
  File "C:\python26\lib\xml\etree\ElementTree.py", line 579, in parse
    source = open(source, "rb")
IOError: [Errno 22] invalid mode ('rb') or filename: '<StringIO.StringIO
instance at 0x00C87A08>'

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