Load a raster layer:
<pre><code>uri = "D:/Python_QGIS/data/dem_subset.tif"
rlayer = iface.addRasterLayer(uri, "my_raster", "gdal")
</code></pre>Check if the raster layer is valid or not:
<pre><code>if rlayer.isValid():
 print("Great this is a valid raster layer!")
else: 
 print("This is invalid raster layer!")
</code></pre>

Load a raster layer:

```
uri = "D:/Python_QGIS/data/dem_subset.tif"
rlayer = iface.addRasterLayer(uri, "my_raster", "gdal")
``` 

Check if the raster layer is valid or not:
```
if rlayer.isValid():
    print("Great this is a valid raster layer!")
else: 
    print("This is invalid raster layer!")
``` 

8- Iterating over a layer

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