arcpy.SelectLayerByAttribute not working with an integer saved in a variable

Question

I have a long code written and this is the last little bit I need and for whichever reason it does not work. This is the simple code.

k=2
arcpy.SelectLayerByAttribute_management("poligon", "NEW_SELECTION", "Id=k")

I tried a lot of different apostrphe, brackets and everything, nothing works. It says a column was specified that does not exist, Error 000358. But when I replace k with a number everything is OK. I'm at a loss of what is wrong.

• Kadir Şahbaz: Try "Id=" + str(k) as where_clause. Or this link can help.
• PolyGeo: Welcome to GIS SE! As a new user be sure to take the Tour. For questions that involve code we ask that you show us where you are stuck with your own code by including a code snippet rather than a copy/paste from your code and the full error message including the line number that results from running that code snippet.
• Michael Stimson: This is because your query is looking for a field called k, which doesn't exist, hence the field not found error. @KadirŞahbaz is correct, you need to put your variable into the statement either with simple concatenation (as shown "Id=" + str(k)) or "Id={}".format(k) to insert the value of the variable into the string; either would work but I suggest that getting some exposure to format statements may benefit you as you move to more complex statements. Perhaps Kadir, you'd like to expand your comment to an answer.
• RJJoling: @KadirŞahbaz Post this as a proper answer with a little explanation on string conversion, so we can give you the proper credits!
• PolyGeo: The where_clause syntax that I prefer is mentioned in @MichaelStimson's comment: "Id={}".format(k) I like that because it is so easily modified when using text fields to "Id='{}'".format(k). I also agree wholeheartedly "that getting some exposure to format statements may benefit you as you move to more complex statements".

Answer 1

Error 000358means "The SQL expression is invalid", as described in Help - ArcGIS Desktop

Your query, "Id=k", means that "get Idand k (field) value of a feature, compare both, if both are equal, select that feature". Since there is no kfield in poligon layer, you encounter an error. Even if k existed as a field, any feature whose Id and kfield are equal would be selected.

But you want to select all features meet Id=2. So, you have to concatenate "Id="string and integer k for where clause.

You can do it in different ways:

k = 2
m = 3
"Id=" + str(k) #1 "Id=2"
"Id=%s" %k #2 "Id=2" old style
"Id={}".format(k) #3 "Id=2" new style
"Id={0}".format(k) # by index
## multiple variables ##
"Id=%s%s" %(k, m) # "Id=23" 
"Id={}{}".format(k, m) # "Id=23" 
# by index, m->0, k->1
"Id={1}{0}_{1}{1}".format(m, k) "Id=23_22" 
"Id=" + k # doesn't work. In Python, you cannot concatenate string
 # and integer in that way unlike some languages do.

• valsten: Thanks for the answer, I have already tried number 1 and number 2 which didn't work for me, but the number three i havent thaught of and it works perfectly.