I'm trying to polygonize. But I'm getting an error message:

'NoneType' object has no attribute 'isMultipart' See log for more details

Basically what I'm trying to do is divide the city into blocks so I can assign a value to each block.

I'm not sure if I'm getting the error because of something about the lines or someting in the attribute table... Or something else.

Here's a closeup of what the street centerlines look like.

enter image description here

Maybe I need to clean up the lines or something, not sure. But anyway here's the error message I get when I run it.

enter image description here

  • 2
    What's the error you encounter? Please edit your question to include the error message text in full (not as an image).
    – Midavalo
    Apr 29, 2017 at 1:28
  • What does the log say?
    – Midavalo
    Apr 29, 2017 at 2:51
  • Actually the log is in the image, that's where the error message is. I'm not sure why the log says to check the log. Unless there's another log I don't know about.
    – GDog
    Apr 29, 2017 at 14:08
  • @GDog It is a classical error message. The problem is clear: there is a feature that is not recognized. Did you follow the steps explained in my answer?
    – mgri
    Apr 29, 2017 at 14:42

3 Answers 3


From Python: Attribute Error - 'NoneType' object has no attribute 'something':

NoneType means that instead of an instance of whatever Class or Object you think you're working with, you've actually got None. That usually means that an assignment or function call up above failed or returned an unexpected result.

This means that there are probably some features (geometries) that are not valid. You may check your input layer using the Check validity algorithm available from the Processing Toolbox and then try again to run the Polygonize tool. It will allow you to repair any eventually invalid geometry.

If it still doesn't work, you may also try the Lines to polygon tool or the Convert lines to polygons SAGA tool, which are both available from the Processing Toolbox.

  • 2
    Comments are not for extended discussion; this conversation has been moved to chat.
    – Midavalo
    Apr 30, 2017 at 2:39
  • I tried the Check Validity tool, and cleaned up any invalid lines I could find, then I used the Convert Lines to Polygons tool and it ran great!
    – Ayla Marie
    Jan 22, 2018 at 20:57

I had similar issue, and discovered that I had lines with a 'NULL' length. I identified these using the field calculator and calculating the $length field, then deleting all lines with a 'NULL' length.

After this the Polygonize tool worked.

  • Can you explain how you did that please? I have the same issue as the OP on here, and I'd like to peruse this line of inquiry to see if this is the answer I need.
    – shawty
    Apr 14, 2018 at 14:08

I had this problem with Point.shp when I tried to calculate X,Y coordinate. I found that ONE empty row was created (by mistake) in the file that actually had no geometry. So I deleted that empty row and then calculated XY.

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