I'm currently trying to iterate through the features of a feature class (using an update cursor, because the goal is to ultimately update the field) and buffer each individual segment. I eventually want to use the buffer in each iteration with different tools, but I can't get the initial Select by Attribute to work. Here's my code:

fc = "Original_Clip"
fcfield = "SEGMENTID"

strt_lyr = arcpy.MakeFeatureLayer_management(fc, "Street_lyr")
with arcpy.da.UpdateCursor(fc, fcfield) as cursor:
     for row in cursor:
        var_segment = row[0]
        print "Buffering segment " + str(var_segment)
        arcpy.SelectLayerByAttribute_management(strt_lyr, "NEW_SELECTION", '{} = \'{}\''.format(var_segment))
        arcpy.Buffer_analysis(strt_lyr, str(var_segment) + "Buff", "20 Feet") 

When I run this code, an error is thrown with the SelectLayerByAttributefunction, saying my where clause is invalid?

Runtime error Traceback (most recent call last): File "", line 15, in File "d:\program files (x86)\arcgis\desktop10.2\arcpy\arcpy\management.py", line 6688, in SelectLayerByAttribute raise e ExecuteError: ERROR 000358: Invalid expression Failed to execute (SelectLayerByAttribute). I'm assuming I just have the SQL syntax wrong (I'm querying a file geodatabase btw), but maybe what I'm trying to do just isn't possible.

  • 1
    You can read "Shape@" in your feature class, and use geometry method to construct the buffer
    – FelixIP
    Oct 3, 2016 at 20:08
  • 2
    Your expression has two placeholders, but you're only passing one in the format method. What is the other variable supposed to be?
    – Evan
    Oct 3, 2016 at 20:25
  • Good catch, it's supposed to be .format(fcfield, var_segment). Oct 3, 2016 at 20:35
  • @AndyFisher does that solve the problem?
    – Midavalo
    Oct 3, 2016 at 20:53
  • @Midavalo, it did not. Oct 3, 2016 at 20:56

1 Answer 1


I've had problems like this with where clauses in SelectLayerByAttribute when I try to build the clause right in the function parameter list. I work around it by building the where clause in a string variable and using the variable in the function parameters instead.

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