[PyQt] TypeError: setLayoutDirection(self, Qt.LayoutDirection): argument 1 has unexpected type 'ProxyMetaclass'

Phil Thompson phil at riverbankcomputing.com
Mon Aug 5 10:22:54 BST 2019

On 04/08/2019 18:45, Kyle Altendorf wrote:
> On 2019-08-04 13:14, Phil Thompson wrote:
>> On 04/08/2019 03:04, Kyle Altendorf wrote:
>>> While reworking my code to correct the errors related to my previous
>>> message I ran into another exception loading .ui files.  This one
>>> doesn't seem to be related to 3.7.4 specifically and I ran my test 
>>> all
>>> the way back to pyqt5.8 with the latest micro for each minor version
>>> failing.
>>> Code and output at:
>>>     https://gist.github.com/altendky/151ddfdab48d566330a2ad8099229153
>>> The traceback ends up at:
>>>       File
>>> "/home/altendky/tmp/venv3.7.4/lib/python3.7/site-packages/PyQt5/uic/properties.py",
>>> line 417, in setProperties
>>>         getattr(widget, 'set%s%s' % (ascii_upper(prop_name[0]),
>>> prop_name[1:]))(prop_value)
>>>     TypeError: setLayoutDirection(self, Qt.LayoutDirection): argument
>>> 1 has unexpected type 'ProxyMetaclass'
>> Putting everything in the one script is probably causing problems, ie.
>> the script that loads the UI also defines the custom widget which
>> means the script is run twice (and maybe it would recurse if there was
>> no exception).
> This started with an error in my real many-file application.  I first
> recreated it in multiple files for the example then compacted down to
> one.  There was recursion because I forgot to add in `if __name__...`
> so I did.  Here is a copy of the example split back into two files.
> https://gist.github.com/altendky/93657f6748a94f1b10316dd4884d65a7

You have to separate the MyWidget implementation from the call to 
loadUiType() so that loadUiType() can be called before loadUi().

The root cause is that loadUiType() is implemented by compiling the XML 
to Python code and then executing that code. The compilation process 
uses proxies for the various PyQt objects.

loadUi() creates the PyQt objects directly (no proxies).

With your code loadUiType() is being called from within loadUi() and 
things get confused.


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