topic Re: Select Layer By Attribute Python Script Tool in Python Questions

Select Layer By Attribute Python Script Tool

JonathanPierre — Wed, 11 Jul 2018 15:50:32 GMT

Hello everyone,

I'm trying to program a simple Select by Attributes Python script tool. I want to be able to find a specific building using a field and zoom in to the location. Also, my tool needs to allow the user to input any field or any value. So far this is what I got.

import arcpy

#Set to current mxd and dataframe
mxd = arcpy.mapping.MapDocument ('CURRENT')
df = arcpy.mapping.ListDataFrames(mxd,"Layers")[0]

# Set overwrite option
arcpy.env.overwriteOutput = True
arcpy.env.workspace ="C:\Users\pierrej\Desktop\GIS Data"

try:
    # Get the input parameters for the Selection Tool
    FClass = arcpy.GetParameterAsText(0)
    Field = arcpy.GetParameterAsText(1)
    Feature = arcpy.GetParameterAsText(2)

# Make a layer from the feature class
arcpy.MakeFeatureLayer_management(FClass,"FclassLayer")

    where_clause = """{} = {}""".format(arcpy.AddFieldDelimiters("FclassLayer", Field),Feature)
    arcpy.AddMessage(where_clause)

    # Select the site
    arcpy.SelectLayerByAttribute_management("FclassLayer","NEW_SELECTION", where_clause)

    # write selected features to a new featureclass
    arcpy.CopyFeatures_management("FclassLayer", "SelectionSites")

    #Zooming to a selection set for the specific layer
    df.zoomToSelectedFeatures()
    df.scale = 2500000
    arcpy.RefreshActiveView()

    # Report a success message
    arcpy.AddMessage("All done!")

except:
     # Report an error messages
     arcpy.AddError("Could not complete")

     # Report any error messages that the tool might have generated
     arcpy.AddMessage(arcpy.GetMessages())

My parameters are the following:

InputFeatureClass = Data Type: Feature Layer, Required, Input, No Multivalue

InputField = Data Type: Field, Required, Input, No Multivalue, Obtained from Input Feature Class

InputValue = DataType: String, Required, No Multivalue

The script runs and I don't have any error message but the tool doesn't select any thing. How can I fix this?

Re: Select Layer By Attribute Python Script Tool

DanPatterson_Retired — Wed, 11 Jul 2018 16:53:52 GMT

Jonathan....

from Select Layer By Attribute—Data Management toolbox | ArcGIS Desktop

FclassLayer should be a variable not a string … dump the quotes

arcpy.SelectLayerByAttribute_management(FclassLayer,"NEW_SELECTION", where_clause)

Re: Select Layer By Attribute Python Script Tool

DarrenWiens2 — Wed, 11 Jul 2018 17:15:09 GMT

I believe you can reference feature layers as strings - they created a feature layer using MakeFeatureLayer. To use as variable, you'd need to set the variable to the output of MakeFeatureLayer.

Jonathan, can you print the where clause, an example of 'Feature', and show the attribute table with a feature that should match the query. The query is likely just not matching anything.

Re: Select Layer By Attribute Python Script Tool

JonathanPierre — Wed, 11 Jul 2018 18:09:36 GMT

Hello Darren, 'Feature' would be the FID #, or the province name for example.

The user enters his feature class layer, specifies the field and enters the field value for the feature we're looking for.

Re: Select Layer By Attribute Python Script Tool

JonathanPierre — Wed, 11 Jul 2018 18:11:14 GMT

    # Get the input parameters for the Selection Tool
    FClass = arcpy.GetParameterAsText(0)
    Field = arcpy.GetParameterAsText(1)
    Feature = arcpy.GetParameterAsText(2)

# Make a layer from the feature class
FclassLayer = arcpy.MakeFeatureLayer_management(FClass,"FclassLayer")

    where_clause = """{} = {}""".format(arcpy.AddFieldDelimiters(FclassLayer, Field),Feature)
    arcpy.AddMessage(where_clause)

    # Select the site
    arcpy.SelectLayerByAttribute_management(FclassLayer,"NEW_SELECTION", where_clause)

    # write selected features to a new featureclass
    arcpy.CopyFeatures_management(FclassLayer, "SelectionSites")

I attributed the layer to a variable called FclassLayer to get rid of the quotation marks. The script still ran but didn't select anything.

Re: Select Layer By Attribute Python Script Tool

Madanbhurati — Wed, 11 Jul 2018 18:41:15 GMT

I would suggest to Add feature class to Map (Table of content), which will be added as feature layer. than use that layer as input for your tool and skip the following line of code. it works fine.

FclassLayer = arcpy.MakeFeatureLayer_management(FClass,"FclassLayer")

Please review following code.

import arcpy
mxd = arcpy.mapping.MapDocument ('CURRENT')
df = arcpy.mapping.ListDataFrames(mxd,"Layers")[0]
arcpy.env.overwriteOutput = True
arcpy.env.workspace ="D:/00-Awork/01-GIS Work/01-ArcGIS/"
wrk=arcpy.env.workspace
arcpy.AddMessage("Workspace added")
FClass = arcpy.GetParameterAsText(0)
Field = arcpy.GetParameterAsText(1)
Feature = arcpy.GetParameterAsText(2)
where_clause = """{} = '{}'""".format(arcpy.AddFieldDelimiters(FClass, Field),Feature) # I have added extra pair of single quotes for selecting strings
arcpy.AddMessage(where_clause)
arcpy.SelectLayerByAttribute_management(FClass,"NEW_SELECTION", where_clause)
arcpy.CopyFeatures_management(FClass, "SelectionSites")
df.zoomToSelectedFeatures()
arcpy.RefreshActiveView()
arcpy.AddMessage("All done!")

Re: Select Layer By Attribute Python Script Tool

JonathanPierre — Wed, 11 Jul 2018 19:12:25 GMT

The extra pair of single quotes gave me a SQL syntax error, so I removed them. This is the code that ended up working but only for numeric fields:

try:
    # Get the input parameters for the Selection Tool
    FClass = arcpy.GetParameterAsText(0)
    Field = arcpy.GetParameterAsText(1)
    Feature = arcpy.GetParameterAsText(2)

    where_clause = """{} = {}""".format(arcpy.AddFieldDelimiters(FClass, Field),Feature)   # I have added extra pair of single quotes for selecting strings
    arcpy.AddMessage(where_clause)

    # Select the site
    arcpy.SelectLayerByAttribute_management(FClass,"NEW_SELECTION", where_clause)

    # write selected features to a new featureclass
    arcpy.CopyFeatures_management(FClass, "SelectionSites")

    #Zooming to a selection set for the specific layer
    df.zoomToSelectedFeatures()
    arcpy.RefreshActiveView()

    # Report a success message
    arcpy.AddMessage("All done!")

However, if I try the tool using a String type field I get an error message. (Invalid expression, and invalid SQL statement was used)