Get NoData value of raster in pyqgis

Question

I'm fighting with pyqgis with a very simple issue. I have a raster layer loaded in my TOC and I'd like to return with python its NoData value.

I looked in the API but (and sure it is my lack) I cannot find a way to do that.

So I get my raster as an object in the console:

rl = iface.activeLayer()

and I tried what I found in some websites (see the list at the bottom):

rl.getNoDataValue() #[1]
Traceback (most recent call last):
  File "<input>", line 1, in <module>
AttributeError: 'QgsRasterLayer' object has no attribute 'getNoDataValue'


rl.noDataValue() #[2] old API
Traceback (most recent call last):
  File "<input>", line 1, in <module>
AttributeError: 'QgsRasterLayer' object has no attribute 'noDataValue'

#[1]: http://qgis.sourceforge.net/qgis_api/html/classQgsRasterLayer.html#a10

#[2]: http://qgis.org/api/1.8/classQgsRasterLayer.html#a558e7f4bb4abe6b95c6882fbe4d2e19f

Look into the QgsRasterLayer class dir(rl) but I cannot find a way to return the NoData values.

Answer 1

That method ('noDataValue') is in QgsRasterBlock class (not in QgsRasterLayer). To get access to this method you can try out this code:

layer = iface.activeLayer()
extent = layer.extent()

provider = layer.dataProvider()

rows = layer.rasterUnitsPerPixelY()
cols = layer.rasterUnitsPerPixelX()

block = provider.block(1, extent,  rows, cols)

print block.noDataValue()

It works for me.