I've created 4 hillshades for a particular area to represent the 4 seasons in a year. The equation I now need to use to determine solar insulation is 1000*hillshade/255 in raster calculator. However, I keep getting this error:

Messages Executing: RasterCalculator "(1000 * "Spring_HS") / 255" "E:\Geog 170\Lab 2\DEM\spring_insul" Start Time: Sat Apr 11 09:44:25 2015 (1000 * Raster(r"Spring_HS")) / 255

ERROR 000539: Error running expression: rcexec() Traceback (most recent call last): File "", line 1, in File "", line 2, in rcexec File "c:\program files (x86)\arcgis\desktop10.2\arcpy\arcpy__init__.py", line 24, in from arcpy.toolbox import * File "c:\program files (x86)\arcgis\desktop10.2\arcpy\arcpy\toolbox.py", line 356, in from management import Graph, GraphTemplate File "c:\program files (x86)\arcgis\desktop10.2\arcpy\arcpy\management.py", line 22, in import _management File "c:\program files (x86)\arcgis\desktop10.2\arcpy\arcpy_management.py", line 14, in import _graph File "c:\program files (x86)\arcgis\desktop10.2\arcpy\arcpy_graph.py", line 27, in import numpy ImportError: No module named numpy

Failed to execute (RasterCalculator). Failed at Sat Apr 11 09:44:25 2015 (Elapsed Time: 0.12 seconds)

I'm not entirely sure what the error message means, but a few people, it seems, determined that it is due to an issue with the raster calculator and arcpy. Please help me to solve this issue or find some kind of work around. Additionally, as a student, it would be great if we could also try to dissect this issue so that I may better understand just what the heck is going on.

It seems that the error code being put out is referring to an issue importing something called "numPy". Here is a duplicate of this question with a slew of different solutions than the solution found in this thread.

  • It means you need to install the Python package numpy, which is numeric library used by a lot of programs under the hood for matrix algebra and the like. Apr 11, 2015 at 17:09
  • I wonder how I managed to install python but not numpy. I was under the impression that both would be installed automatically with ArcGIS. Either way, I'll test this out by switching to a computer at school (I'm sure they installed everything correctly as opposed to a novice like me). Thank you and I will update you and really anyone else who runs into this issue. Additionally, I think this post is technically a duplicate, however the solutions there did not work for me. Thank you both!
    – George
    Apr 11, 2015 at 18:28
  • @George, I would have attach a link to the duplicate in your quesion; in particular in the line in which you state thah: "...but a few people, it seems, determined that it is due...". In addition, if you could elaborate on what you've done to solve your issue, i.e. using map-algebra, to show that this is indeed a distinct question.
    – dof1985
    Apr 11, 2015 at 19:15
  • hi dof1985, sorry for the lack of clarification the first time around. The people I was referring to were actually my peers in class, who are also as confused with this process as well. However, it is confirmed, the issue was in numPy! The computers at my schools lab have it installed and everything is running smoothly! Thank you both very much!
    – George
    Apr 11, 2015 at 19:28
  • 1
    @dof1985 Thanks! Yes, this actually makes it easier to direct comments towards specific people. In regards to this question being a duplicate, I see what you mean. Let me try editing my original question. I'll see if I can grab a tutorial for the installation of numPy as well.
    – George
    Apr 11, 2015 at 19:54

1 Answer 1


Thank you @dof1985 and @John Barca. Importing numPy was the issue here. Please refer to the link within the question to view essentially the same question (sorry for the duplicate everyone) with alternate solutions. The solution here was pretty much me moving to another computer that had correctly installed ArcGIS. I believe numPy on my home computer is corrupted or non-existent; therefore a re-installation is coming.

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