topic Re: Expression for select by attribute in Python Questions

Expression for select by attribute

NaimeCelik — Tue, 28 Apr 2015 11:49:50 GMT

Hello, I have unique list like ProcessedData=["Line1","Line17","Line76"....] and I have a point data in which every point has the line name they belong to in its attribute table. I want to select those points based on their line names but only the ones in that unique list. I am applying the python code below but processing is very slow. I need to select 10000 lines and the process is very slow with the code below. Is there any other way of writing the expression so that it selects them in same time instead of one by one in a for loop ?

for item in ProcessedData:

Expression= "\"LineName\" = "+ "'"+item+"'"

arcpy.SelectLayerByAttribute_management ("PointData", "ADD_TO_SELECTION", Expression)

Re: Expression for select by attribute

JakeSkinner — Sat, 11 Dec 2021 23:40:50 GMT

Hi Naime,

Instead of iterating through your list with a 'for' loop, try using 'IN' within your expression to select multiple values. Ex:

list = ['Alabama', 'Arizona']
list = str(list)[1:-1]
expression = "State_Name IN (" + list + ")"

arcpy.SelectLayerByAttribute_management("COUNTIES", "NEW_SELECTION", expression)

Re: Expression for select by attribute

NaimeCelik — Wed, 29 Apr 2015 08:05:36 GMT

Hello Jake,

Thank you for your reply.

When I inserted my expression as you indicated

ProcessedData = str(ProcessedData)[1:-1]

expression = "LineName (" + ProcessedData+ ")"

I got error as below, why do you think this happens?

ERROR 000358: Invalid expression

Failed to execute (SelectLayerByAttribute)

Re: Expression for select by attribute

NaimeCelik — Wed, 29 Apr 2015 08:25:51 GMT

I also tried

ProcessedData = str(ProcessedData)[1:-1]

expression = "LineName IN (" + ProcessedData+ ")"

still same error

Re: Expression for select by attribute

NaimeCelik — Wed, 29 Apr 2015 08:45:19 GMT

Hello Jake

I just realized that the problem was encoding in the list items were look like u'Line1' after turning each item

ProcessedData=[str(x) for x in ProcessedData]

then it worked very well Thank you so much for your answer