I'm a total beginner at programming and Python. I'm trying to select features by attributes and then field calculate in another field.
In VBA it might look like this:
If [Z1COMM] = "R" then [Z1UNITS] = [Z1RUNTS] and [Z1SIZE] = [Z1RSIZE] ElseIf [Z1COMM] = "O" then [Z1UNITS] = [Z1OUNTS] and [Z1SIZE] = [Z1OSIZE] Else [Z1UNITS] = [Z1RUNTS] and [Z1SIZE] = [Z1SIZE] End If
I could probably do this pretty easily in VBA using the code block in the field calculator but I want to start grasping Python more. Here's what I got from trying to make a list of the values as a first step (taken and modified from http://support.esri.com/en/knowledgebase/techarticles/detail/41442):
# Import modules import arcpy, os , sys, string # Create environmental variables arcpy.env.overwriteOutput = True arcpy.env.workspace = r"J:\CO_004" # Set variables input = "testfile.shp" lyr = "tst_layer" arcpy.MakeFeatureLayer_management(input,lyr) outFile = open(r"J:\CO_004\test.text", "w") # Build search cursor fcSearch = arcpy.da.SearchCursor(lyr, ["Z1COMM"]) for fcRow in fcSearch: # Process: Select by attributes arcpy.SelectLayerByAttribute_management(lyr, "NEW_SELECTION", "Z1COMM" == 'O') txtSearch = arcpy.da.SearchCursor(lyr, ["Z1COMM"]) outFile.write("Commodity: " + str(fcRow) + "\n") for txtRow in txtSearch: zval = str(txtRow) outFile.write(zval + "\n") outFile.close() #This closes the text file del input, lyr, fcRow, txtRow, txtSearch, fcSearch, outFile, zval
And this is my latest error: ExecuteError: ERROR 000358: Invalid expression Failed to execute (SelectLayerByAttribute).
I originally tried to use a feature class for the input to avoid this part of the code: lyr = "tst_layer" arcpy.MakeFeatureLayer_management(input,lyr)
But got an error that feature classes could not be used. If I have to make a separate shapefile so be it but it's be more convenient to work straight from a feature class in a file GDB.
I'm mainly confused by this part:
arcpy.SelectLayerByAttribute_management(lyr, "NEW_SELECTION", "Z1COMM" == 'O')
where the last parameter I thought should be the selection criteria.
Also, this code just makes a txt file, it doesn't actually calculate anything but I thought once I figured this out I could take the next step.