Good morning,

I use the latest version of QGIS (Lyon) in MAC and have se the default Python version 2.7. Moreover, I have installed all the required python modules and GDAL.

It was working before, but now, when I click on the "Browse" button in Vector-> Geoprocessing->Union, it returns the following error (actually, it returns this error whenever I click on any "browse" button in QGIS):

Error during execution of Python code :

TypeError: QgsEncodingFileDialog(QWidget parent=None, QString caption=QString(), QString directory=QString(), QString filter=QString(), QString encoding=QString()): argument 3 has unexpected type 'QPyNullVariant' 
Traceback (most recent call last):
  File "/Applications/QGIS.app/Contents/Resources/python/plugins/fTools/tools/doGeoprocessing.py", line 125, in outFile
    (self.shapefileName, self.encoding) = ftools_utils.saveDialog(self)
  File "/Applications/QGIS.app/Contents/Resources/python/plugins/fTools/tools/ftools_utils.py", line 327, in saveDialog
    fileDialog = QgsEncodingFileDialog(parent, QCoreApplication.translate("fTools", "Save output shapefile"), dirName, filtering, encode)
TypeError: QgsEncodingFileDialog(QWidget parent=None, QString caption=QString(), QString directory=QString(), QString filter=QString(), QString encoding=QString()): argument 3 has unexpected type 'QPyNullVariant'


Versione Python: 2.7.10 (default, Oct 23 2015, 18:05:06) [GCC 4.2.1 Compatible Apple LLVM 7.0.0 (clang-700.0.59.5)] 
Versione di QGIS: 2.12.1-Lyon Lyon, exported 


I cannot enter the path manually. It does not allow me to click in the blank field.

Thanks for every answer,
Marta

This appears to be an issue with the QGis application and not a problem with Python itself.

See the following URL for support on QGis: <http://www.qgis.org/en/site/forusers/support.html>

Regards,

  Ronald

Not a bug in *Python*.