Still having problems stepping through a list inside of a tool

JohnNunnali · ‎04-05-2012

I had started a thread about a month ago on this same topic but want to start again at the beginning.

I am attempting to iterate through a list inside of the SelectLayerByAttributes tool in ArcPy. My goal is to be able to select attributes from a field (column), export the current map view with the selected attributes as a jpeg, clear the selection, and then start the process again for a different field. I am currently trying to run all three steps within a loop. My issue is that I can not figure out how to make the SelectLayerByAttributes tool step to the next field name after the first completes. Currently the loop runs but just keeps selecting the values from the initial field and not changing to the next in the list. I have attached an example of how the data is setup.

I am trying to select for values greater than zero for each column, then export the results, clear the selection, and them move to next column.

The code currently looks like this:

#Script to create distribution maps for wetland species
#Import arcpy and set workspace
import arcpy
import arcpy.mapping
arcpy.env.workspace = r"P:\CoWetlandTools\maps\distribution_maps_Johns_pytest"
import arcpy.sa
#generate a list
speciesList =("Achillea_millefolium", "Acroptilon_repens", "Actinea_osterhoutii")

#Create Loop and List to run processing for
for species in speciesList:

  #select counties each species is known to occur  
  arcpy.SelectLayerByAttribute_management ("counties_edited_datamergetest", "NEW_SELECTION", "'Achillea_milefolium' > '0'")

  #Export selected to jpeg
  mxd = arcpy.mapping.MapDocument(r"CURRENT")
  
  arcpy.mapping.ExportToJPEG(mxd, r"P:\CoWetlandTools\maps\Achillea_milefolium.jpg")

  #clear selected attributes
  arcpy.SelectLayerByAttribute_management ("counties_edited_datamergetest", "CLEAR_SELECTION")

#finished
print "Finished"

Where I need help is in the where clause of the arcpy.SelectLayerByAttribute_management function and the arcpy.mapping.ExportToJPEG function.

Any suggestions are greatly appreciated.

KevinHibma · ‎04-05-2012

Try this for your select statement:

arcpy.SelectLayerByAttribute_management("counties_edited_datamergetest", "NEW_SELECTION",  "'" + str(species) + "' > 0  "  )

JohnNunnali · ‎04-05-2012

Hmmmm.....I was able to make it work for a single species. I need to have the workspace as an mxd because I am exporting the "current" view with the attributes selected to a jpeg.

Any suggestions?

JohnNunnali · ‎04-05-2012

@Kevin

I tried your code line and still received the following error:

Runtime error <class 'arcgisscripting.ExecuteError'>: ERROR 000358: Invalid expression Failed to execute (SelectLayerByAttribute).

This is my current code:

#Script to create distribution maps for wetland species
#Import arcpy and set workspace
import arcpy
import arcpy.mapping
arcpy.env.workspace = r"P:\CoWetlandTools\maps\distribution_maps_Johns_pytest.mxd"
import arcpy.sa
#generate a list
speciesList =("Achillea_millefolium", "Acroptilon_repens", "Actinea_osterhoutii")


#Create Loop and List to run processing for
for species in speciesList:
  print species   
  #select counties each species is known to occur  
  arcpy.SelectLayerByAttribute_management ("counties_edited_datamergetest", "NEW_SELECTION",  '"' + str(species) + '"  > 0')

  #Export selected to jpeg
  mxd = arcpy.mapping.MapDocument(r"CURRENT")
  
  arcpy.mapping.ExportToJPEG(mxd, r"P:\CoWetlandTools\maps\"'" + str(species) + "'.jpg")

  #clear selected attributes
  arcpy.SelectLayerByAttribute_management ("counties_edited_datamergetest", "CLEAR_SELECTION")

#finished
print "Finished"

BruceNielsen · ‎04-06-2012

Try using this:

arcpy.SelectLayerByAttribute_management ("counties_edited_datamergetest", "NEW_SELECTION", "\"%s\" > 0" % species)

JohnNunnali · ‎04-10-2012

@ Bruce

I tried your suggestion but received the same error I received with the other formats:

Runtime error <class 'arcgisscripting.ExecuteError'>: ERROR 000358: Invalid expression Failed to execute (SelectLayerByAttribute).

I have re-worked my code some and I am now using arcpy.ListFields to define the fields I want to make the selections in. I just can't seem to figure out the reason why the SQL expression in the SelectLayerByAttribute function is invalid. I know that the field list is generating properly because when testing I was able to successfully print the desired field names.

Any thoughts or suggestion are much appreciated.

Here is my current code:

#Script to create distribution maps for wetland species
#Import arcpy and set workspace
import arcpy
import arcpy.mapping
arcpy.env.workspace = r"P:\CoWetlandTools\maps\distribution_maps_Johns_pytest.mxd"
import arcpy.sa


#list object that is the list of fields in our table
#List fields and generate a list

fields = arcpy.ListFields(r"Y:\John_N\Wetland_field_guide_distribution_maps\counties_edited_datamergetest_export.shp", None , "Double")


#select fieldname1 > 0

#Create Loop and List to run processing for
for field in fields:
  
  #select counties each field has attribute values > 0
  #select field1 > 0
  arcpy.SelectLayerByAttribute_management ("counties_edited_datamergetest", "NEW_SELECTION",  "'" + str(field) + "'" ' > 0')

  # export current to jpg such that the name of the file is field1
  mxd = arcpy.mapping.MapDocument(r"CURRENT")
  
  arcpy.mapping.ExportToJPEG(mxd, r"P:\CoWetlandTools\maps\"'" + str(field) + "'.jpg")

  #clear selected attributes
  arcpy.SelectLayerByAttribute_management ("counties_edited_datamergetest", "CLEAR_SELECTION")

#finished
print "Finished"

JohnNunnali · ‎04-11-2012

I have made a little progress. I used pythonWin to debug the program and finally have more info on why the script is failing at the SelectLayerByAttribute step. The error is as follows:

Traceback (most recent call last):
File "C:\ESRI\Python26\ArcGIS10.0\Lib\site-packages\pythonwin\pywin\framework\scriptutils.py", line 309, in RunScript
    debugger.run(codeObject, __main__.__dict__, start_stepping=0)
File "C:\ESRI\Python26\ArcGIS10.0\Lib\site-packages\pythonwin\pywin\debugger\__init__.py", line 60, in run
    _GetCurrentDebugger().run(cmd, globals,locals, start_stepping)
File "C:\ESRI\Python26\ArcGIS10.0\Lib\site-packages\pythonwin\pywin\debugger\debugger.py", line 624, in run
    exec cmd in globals, locals
File "Y:\John_N\From_desktop\python_training_scripts\dist_map_test1.py", line 22, in <module>
    arcpy.SelectLayerByAttribute_management (r"Y:\John_N\Wetland_field_guide_distribution_maps\counties_datamergetest_export2.lyr", "NEW_SELECTION", '"' + str(field) + '" ' > 0)
File "C:\ESRI\ArcGIS\Desktop10.0\arcpy\arcpy\management.py", line 4259, in SelectLayerByAttribute
    raise e
ExecuteError: Failed to execute. Parameters are not valid.
ERROR 000825: The value is not a layer or table view
ERROR 000840: The value is not a Raster Layer.
ERROR 000840: The value is not a Mosaic Layer.
Failed to execute (SelectLayerByAttribute).

I saved the shapefile I was using as a layer file and tried to use that path but receive the same error. Am I missing something or incorrectly saving as a layer file?

DarrenWiens2 · ‎04-11-2012

Your where statement must be entirely enclosed in single quotes. Your field name must be enclosed in double quotes.

' " ' + str(field) + ' " > 0 '

Also, reference the layer in your map ("counties_edited_datamergetest"), not the .lyr file.

DarrenWiens2 · ‎04-11-2012

OK, this problem was frustrating me so I actually tried it. Here's a copy that works for my mxd named "junk" and a file named "file". Change as appropriate.

import arcpy
mxd = arcpy.mapping.MapDocument(r"H:\GIS_Data\junk.mxd")
fields = arcpy.ListFields(r"H:\GIS_Data\TEMP.gdb\file", None , "SmallInteger")
for field in fields:
    for lyr in arcpy.mapping.ListLayers(mxd, "file", arcpy.mapping.ListDataFrames(mxd)[0]):
        arcpy.SelectLayerByAttribute_management (lyr, "NEW_SELECTION",  '"' + field.name + '" > 0')
        arcpy.mapping.ExportToJPEG(mxd, r"H:\GIS_Data\map_" + field.name + ".jpg")
        arcpy.SelectLayerByAttribute_management (lyr, "CLEAR_SELECTION")

JohnNunnali · ‎04-11-2012

The last suggestion appears to solve the invalid expression issue I was having in the SelectLayerByAttribute function. The script now returns no error messages when running it through the PythonWin debugger. However when executing it no records are selected. It appears it successfully reads all lines in the code because it prints "finished" however it seems to exit the loop without selecting any features. The current code is:

#Script to create distribution maps for wetland species
#Import arcpy and set workspace
import arcpy
import arcpy.mapping
mxd = arcpy.mapping.MapDocument (r"P:\CoWetlandTools\maps\distribution_maps_Johns_pytest.mxd")

#list object that is the list of fields in our table
#List fields and generate a list

fields = arcpy.ListFields(r"Y:\John_N\Wetland_field_guide_distribution_maps\counties_datamerge.gdb\counties_edited_datamergetest" , None , "Double")

#select fieldname1 > 0

#Create Loop and List to run processing for
for field in fields:
  for lyr in arcpy.mapping.ListLayers (mxd, "file" , arcpy.mapping.ListDataFrames (mxd) [0]):
    #select counties each field has attribute values > 0
    #select field1 > 0
    arcpy.SelectLayerByAttribute_management (lyr, "NEW_SELECTION", '"' + field.name + '"  > 0')

    # export current to jpg such that the name of the file is field1
    arcpy.mapping.ExportToJPEG(mxd, r"P:\CoWetlandTools\maps\map_ " + field.name + ".jpg")

    #clear selected attributes
    arcpy.SelectLayerByAttribute_management (lyr, "CLEAR_SELECTION")

#finished
print "Finished"

I tried with the data in a shapefile and a personal geodatabase with similar results.

All suggestions are greatly appreciated.

DarrenWiens2 · ‎04-11-2012

for lyr in arcpy.mapping.ListLayers (mxd, "file" , arcpy.mapping.ListDataFrames (mxd) [0]):

The above line means, "list all of the layers named 'file' from the first data frame in the map, 'mxd' ". Change 'file' to be the name of your layer in the map.