topic Error 000358: Invalid Expression when trying to select layer by attribute in Python Snippets Questions

Error 000358: Invalid Expression when trying to select layer by attribute

TiffanieLaw — Tue, 21 Aug 2018 17:04:51 GMT

I'm creating a script where I'm trying to select all the null values based on a specific field. The feature is joined with another feature, thus altering the title of fields to be FeatureName_FieldName. I want to keep these titles as I will be exporting the table and if I set qualified field names to False, the fields won't be able to be properly interpreted.

mayDevice = mayFeature+"_"+"DEVICE_ID"

whereClause = mayDevice "IS NULL"

arcpy.SelectLayerByAttribute_management(mayFeature, "NEW_SELECTION", whereClause)

I don't know how to include a variable in an "is null" expression.

Re: Error 000358: Invalid Expression when trying to select layer by attribute

DanPatterson_Retired — Tue, 21 Aug 2018 17:15:33 GMT

Some suggestions Tiffanie:

print the query out to check what it looks like

do one manually and copy the result

check SQL reference for query expressions used in ArcGIS—ArcGIS Pro | ArcGIS Desktop there is an example there

Re: Error 000358: Invalid Expression when trying to select layer by attribute

RandyBurton — Sun, 12 Dec 2021 10:20:50 GMT

Your whereClause as shown is missing a + sign and space before " IS NULL". When joining strings, I like to use .format as I find the code is a bit clearer. You might try something like:

mayDevice = "{}_DEVICE_ID".format(mayFeature)

whereClause = "{} IS NULL".format(mayDevice)‍‍‍