I have been working on QGIS 3.10, I am using DEMs files that come originally from Lidar data, so they are large files with high resolution. I have been trying to create contours using the: Raster, Extraction, contour option. The problem is that my laptop crashes when I change the default elevation from 10 to 2. I originally thought that the problem could be related to memory. However, I upgraded the RAM memory and internal memory of my computer and it still crashes. The last time it went pretty bad and a blue screen appeared. I turn off my laptop and this error message appear after I turned on the laptop and I restarted Qgis:

ValueError: embedded null byte

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "", line 1, in 
  File "C:/PROGRA~1/QGIS 3.10/apps/qgis-ltr/./python\qgis\utils.py", line 42, in 
    import time
SystemError:  returned a result with an error set

Python version:
3.7.0 (v3.7.0:1bf9cc5093, Jun 27 2018, 04:59:51) [MSC v.1914 64 bit (AMD64)]

QGIS version:
3.10.7-A Coruña 'A Coruña', 7b4ca4c8d0

Python path:
['C:/PROGRA~1/QGIS 3.10/apps/qgis-ltr/./python', 'C:/Users/Gaby/AppData/Roaming/QGIS/QGIS3\\profiles\\default/python', 'C:/Users/Gaby/AppData/Roaming/QGIS/QGIS3\\profiles\\default/python/plugins', 'C:/PROGRA~1/QGIS 3.10/apps/qgis-ltr/./python/plugins', 'C:\\PROGRA~1\\QGIS 3.10\\apps\\Python37', 'C:\\PROGRA~1\\QGIS 3.10\\apps\\Python37\\Scripts', 'C:\\Program Files\\QGIS 3.10\\bin\\python37.zip', 'C:\\PROGRA~1\\QGIS 3.10\\apps\\Python37\\DLLs', 'C:\\PROGRA~1\\QGIS 3.10\\apps\\Python37\\lib', 'C:\\Program Files\\QGIS 3.10\\bin', 'C:\\PROGRA~1\\QGIS 3.10\\apps\\Python37\\lib\\site-packages', 'C:\\PROGRA~1\\QGIS 3.10\\apps\\Python37\\lib\\site-packages\\win32', 'C:\\PROGRA~1\\QGIS 3.10\\apps\\Python37\\lib\\site-packages\\win32\\lib', 'C:\\PROGRA~1\\QGIS 3.10\\apps\\Python37\\lib\\site-packages\\Pythonwin'] `

I also kept in my laptop the older and more stable version of QGIS 2.18 and I extracted contours of the same file....No problem at all.

Does anyone have had a similar problem regarding extracting contours?

  • Give us a sense of the scope of the task: How large an area, and what resolution is the raster data?
    – Bjorn
    Jul 2, 2020 at 14:53

1 Answer 1


Sounds similar to:


Which is a Python3 issue, which would explain why QGIS 2.18 would not have the issue (It uses Python 2.7).

I would raise this as a bug report on:


But there is likely something else going, on as the answers suggest that it is a file name issue, not a file issue.

You could try removing any spaces from the filename.

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