I have the following error message every time I try to run a GRASS algorithm in QGIS 3.4. I unistalled the software and installed it again but I did not solve anything.

Traceback (most recent call last):
File "C:/PROGRA~1/QGIS3~1.4/apps/qgis/./python/plugins\processing\algs\grass7\Grass7Algorithm.py", line 415, in processAlgorithm
Grass7Utils.executeGrass(self.commands, feedback, self.outputCommands)
File "C:/PROGRA~1/QGIS3~1.4/apps/qgis/./python/plugins\processing\algs\grass7\Grass7Utils.py", line 372, in executeGrass
for line in iter(proc.stdout.readline, ''):
File "C:\PROGRA~1\QGIS3~1.4\apps\Python37\lib\codecs.py", line 322, in decode
(result, consumed) = self._buffer_decode(data, self.errors, final)
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xe8 in position 50: invalid continuation byte
  • Similar topic Error using v.clean – Taras Nov 13 '18 at 14:24
  • I was experiencing the same issue. Luckily, the answer provided by Mike worked for me. Thanks! – Friedemann Nov 22 '18 at 13:54
  • This does not really answer the question. If you have a different question, you can ask it by clicking Ask Question. You can also add a bounty to draw more attention to this question once you have enough reputation. - From Review – Hornbydd Nov 22 '18 at 14:41

Try adjusting the file: ..\apps\qgis\python\plugins\processing\algs\grass7\Grass7Utils.py at line 370:

        startupinfo=si if isWindows() else None,
        encoding = 'cp850' if isWindows() else None # new encoding for DOS
) as proc:


            startupinfo=si if isWindows() else None,
            encoding = 'cp850' if isWindows() else None # new encoding for DOS
    ) as proc:

Background: The console (stdout, stderr) speaks "DOS". An MSDOS non ASCII char in the output causes the code to crash.

Note: In https://github.com/qgis/QGIS/tree/master/python/plugins/processing/algs/grass7 there is a new Version. If also an "decode" error occurs in the new version, it is probably due to a faulty GRASS installation. Check the grass74.bat file.

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  • I'm not encountering an error anymore, after adjusting the code. But know QGIS gets stuck. Always after the logfile says: "No attribute table was found [...] x features without category were written". Even though an attribute table exists and it also happens with different inputs. – gHupf Nov 14 '18 at 8:32
  • Try my new Adaptation´. You can also try the new Version on github.com/qgis/QGIS/tree/master/python/plugins/processing/algs/…. – Mike Nov 14 '18 at 11:00
  • Now the processing plugin can't be loaded due to a syntax error. I think it points to the word encoding. – gHupf Nov 14 '18 at 14:29
  • Is there a ticket tracking this issue? – Gnafu Nov 16 '18 at 9:17
  • yes please, create also a QGIS issue we can't rely on a third party platform as stackexchange the trace of a bugfix – Luigi Pirelli Nov 20 '18 at 21:10

QGIS version 3.4.2:

The new QGIS version 3.4.2 fixes this bug. You should not encounter any more error messages.

Note: This only works since QGIS version 3.4.2, if you use a previous version of 3.x please update QGIS or check the other answer(s) for possible workarounds.

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