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I have the same problem as Making QGIS layer update from changed data source.

However, I cannot get the solution proposed by Matthias Kuhn in a comment on an answer to that question to work.

I am using QGIS 3.4, I have loaded a .geojson file as a vector layer and am trying to refresh it without removing and re-adding. The map refreshes when I move it but the attribute table is not re-loaded. I may not have understood how to use the reload function so here are my steps, I am using the Python Console.

       mc = iface.mapCanvas()
       layer = mc.currentLayer()
       layer.name()
       'radarOutGJTemp'  #--- Correct

       # Tried the following with errors attached
       layer.dataProvider().reload()
AttributeError: 'QgsVectorDataProvider' object has no attribute 'reload'  

       layer.dataProvider.reload('radarOutGJTemp')
AttributeError: 'builtin_function_or_method' object has no attribute 'reload'  

       layer.dataProvider.reload(radarOutGJTemp)
AttributeError: 'builtin_function_or_method' object has no attribute 'reload'

I can see the function reload appear in a window as I type. I did try to import reload just in case, that failed but again I could see it appear in the window as I typed.

import reload
ModuleNotFoundError: No module named 'reload'
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  • 1
    The method reload() belongs to the QgsRasterDataProvider class. You are working with a QgsVectorDataProvider object. This class has the method forceReload(). Did you try that?
    – Ben W
    Jun 7, 2020 at 22:02
  • Your answer makes sense, I had not realised. I think I may be missing something basic, this is my first attempt at Python in Qgis although I am programming in Python.
    – Roo
    Jun 8, 2020 at 7:38
  • I get AttributeError: 'builtin_function_or_method' object has no attribute 'forceReload' for all variations of the line. I can select the function so it does exist. I had missed the first setup step from my question so will add it to the code above.
    – Roo
    Jun 8, 2020 at 7:46
  • 1
    That suggests that you didn't include the parentheses after dataProvider() needed to actually call the method, layer.dataProvider().forceReload() should work. However, I see that forceReload() is deprecated and will be removed in Qgis 4. So you could use the reloadData() method inherited by all subclasses of QgsDataProvider. E.g. layer.dataProvider().reloadData(). I haven't tested mind you- I'm just going off the docs.
    – Ben W
    Jun 8, 2020 at 8:05
  • That was it, I am sorry, parenthesis were missing. I will do a bit more testing and post an update.
    – Roo
    Jun 8, 2020 at 8:48

1 Answer 1

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With help from @BenW, the following lines refresh my map when I run them in the QGIS Python console using QGIS v3.4.

  mc = iface.mapCanvas()
  layer = mc.currentLayer()
  layer.dataProvider().reloadData()
  layer.triggerRepaint()

The final step is explained in the following post.
Does mapCanvas().refresh() not work in QGIS 2.6?

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