What is the proper way to do for and if statements in python?

Question

I am having issues with loops and if statements in python. I keep getting an error on the last line. What am I doing wrong? import arcpy from arcpy.sa import * from arcpy import env sorder=r"C:\Temp\ARCGIS_PROJECT\Tutorial\Final\layers\streamorder" desc= arcpy.Describe(sorder) xmin= desc.extent.XMin ymin=desc.extent.YMin xmax= desc.extent.XMax ymax= desc.extent.YMax count= 0 for columns in range (xmin, xmax): pointval= arcpy.GetCellValue_management(sorder,"%s %s" % (columns++,ymin), "1") if (pointval== 1, pointval==2, pointval==3): count++ print "count= %s" % (count)‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

XanderBakker · Answer

Below an example of using a numy array to get the values you are interested in: The blue pixel have the value we are interested in (in my case 0). The red boxes are the points that are being created by the code below. In your case line 21 would be something as proposed by Dan_Patterson: if val in (1, 2, 3): import arcpy def main(): arcpy.env.overwriteOutput = True ras_path = r'C:\GeoNet\WUE2\r007_WUE.TIF' # ourput featureclass fc_out = r'C:\GeoNet\WUE2\points.shp' # convert to numpy amd determine the sizes ras_np = arcpy.RasterToNumPyArray(ras_path) rows = ras_np.shape[0] cols = ras_np.shape[1] raster = arcpy.Raster(ras_path) points = [] row = rows-1 for col in range(cols): val = ras_np[row, col] if int(val) == 0: pntg = CreatePointGeometry(raster, row, col) points.append(pntg) arcpy.CopyFeatures_management(points, fc_out) def CreatePointGeometry(raster, row, col): xcell = raster.meanCellWidth ycell = raster.meanCellHeight xmin = raster.extent.XMin ymax = raster.extent.YMax sr = raster.spatialReference pnt = arcpy.Point((col + 0.5) * xcell + xmin, ymax - (row + 0.5) * ycell) return arcpy.PointGeometry(pnt, sr) if __name__ == '__main__': main()‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

XanderBakker · Answer

Hi Andrew Martin ,

I guess that this is (any many more questions you have posted during the past days are) still related to this challenge:

How do you create point shapefiles on a raster to create watersheds?

Maybe it would be a lot easier to extract the last line of the raster (Extract by Rectangle—Help | ArcGIS Desktop ) and use some raster algebra (What is Map Algebra?—ArcGIS Help | ArcGIS Desktop ) to set the values that you are not interested in to NoData like:

new_raster = Con(ori_raster <= 3,  ori_raster)

... and than simply convert the raster to points: Raster to Point—Help | ArcGIS Desktop

This would result in a point featureclass with the points you are looking for.

Another method is to use convert the raster (or subset of the raster) to numpy array and read out the last line, test for the raster value and populate a point featureclass with the result.

DanPatterson_Retired · Answer

You shouldn't do comparisons like you are... use 'in' ... it is much cleaner, assuming that these are the only values you have. pointval = 2 if pointval in (1, 2, 3): print("yes") else: print("no") yes‍‍‍‍‍‍‍‍‍‍‍‍‍ and you can mix object types pointval = 'two' if pointval in (1, 2, 'two', 3): print("yes") else: print("no") yes‍‍‍‍‍‍‍‍