Question: SelectLayerByAttributeManagement

[Lew.Gr...@gov.bc.ca]

Hi Pythoneers,

 

I am trying to select attributes from a layer that has 1639 records.  In this case I am selecting 'FIRESTATUS <> \'Out\'')

 

        arcpy.SelectLayerByAttribute_management(layerName, "NEW_SELECTION", 'FIRESTATUS <> \'Out\'')       
        result = int(arcpy.GetCount_management(layerName).getOutput(0))

 

 

 

It should return 345 records but it returns all of them (1639 records).

 

When I try a different selection, say   'FIRESTATUS <> \'Mop-up\'' , it again return 1639 records instead of a subset of records.

 

All the SQL statements used run without error messages.

 

Any thoughts on what I am overlooking are appreciated please.

 

Thanks

Lew

 

 

[Steinke, Candice FLNR:EX]

Hi Lew,

In my experience it works best to save the expression as a variable prior to your select by statement and then call the variable instead of having the expression in the select statement......

 

selFire = “FIRESTATUS <> ‘Out’”

arcpy.SelectLayerByAttribute_management(layerName, “NEW_SELECTION”,selFire)

 

Not sure if that will solve your issue or not?

 

Candice Steinke
GIS/Data Analyst
BC Timber Sales - Kamloops TSO
1265 Dalhousie Drive
Kamloops, BC V2C 5Z5
Phone: 250-371-4450
Fax: 250-371-6565

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[Greentree, Lew FLNR:EX]

Hi Pythoneers,

 

The solution to this was to create a Feature Layer first.  I

 

 

def selection():

        if arcpy.Exists(layerName):

            print "Deleting outLayer"

            arcpy.DeleteFeatures_management(layerName)

   

        arcpy.MakeFeatureLayer_management(tmp_layername,layerName)

        arcpy.SelectLayerByAttribute_management(layerName, "NEW_SELECTION", 'FIRESTATUS <> \'Out\'')       

        result = int(arcpy.GetCount_management(layerName).getOutput(0))

        print "+++++++++++++++++++++++++++++++++++++++++++"

        print layerName

        print result       

        print "+++++++++++++++++++++++++++++++++++++++++++"

 

 

... Result = 345

 

Cheers

Lew

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[Mike Neal]

Just a note about your code:  To delete a layer, rather than the features IN the layer, you need to get a handle first, then delete the handle:

 

myLayer = arcpy.MakeFeatureLayer_management(tmp_layername,layerName)

arcpy.Delete_management(myLayer)

 

This is how you can release layer locks too, if you want to delete an FGDB you were working on or something higher level like that in a script.

 

Cheers,

Mike

[Steinke, Candice FLNR:EX]

Hi Mike,

I am working on a script right now where I’m trying to delete a FGDB at the end of my process, but I keep running into lock issues.

Can you explain how that would work?  Do I have to use Delete_management to first delete all of the feature classes and feature layers associated with the FGDB before it will unlock and allow me to delete it?

 

Candice Steinke
GIS/Data Analyst
BC Timber Sales - Kamloops TSO
1265 Dalhousie Drive
Kamloops, BC V2C 5Z5
Phone: 250-371-4450
Fax: 250-371-6565

[Greentree, Lew FLNR:EX]

Hi Candice,

 

A solution is offered by one of the comments in this thread.

 

http://forums.arcgis.com/threads/7904-Can-t-delete-a-file-GDB-in-Python-Script-Tool

 

Also, as it appears that you are creating a temporary FGDB, could you not just create it on the E drive and have it automatically deleted at reboot or log-off?

[Mike Neal]

Hi Candice,

 

You won't have to delete each item in the FGDB before deleting the whole thing IF you clean up all the processes you run along the way.  So any time you open a cursor, the cursor needs to be deleted.  Any time you create a layer (feature or table), you need to delete the layer as soon as you are done with it.  And you can't have ArcMap, ArcCatalog, or any of the other tools (Server, ArcScene, etc. can all be culprits) open and looking at that data either.  Depending on workflow it can be easier to simply designate a temp directory, create your FGDB using a random number or a uuid or something, and just clean that out from time to time when nothing is running.  Unfortunately this concurrency stuff can get tricky if you have complicated workflows.

 

Good Luck!

Mike

[Steinke, Candice FLNR:EX]

Thanks Mike.  I generally try to clean up as I go but I’ve probably missed a few things.......this one seems to only intermittently give me grief so it’s frustrating because one time it works and the next it doesn’t!

[Mike Neal]

I hear you!

 

Try something like this, it allows the system to catch up, especially with a network share:

 

import time

 

while arcpy.Exists_management(FGDB):

    try:

        arcpy.Delete_management(FGDB)

    except:   

        time.sleep(10)