1

I am defining a function for use in a ArcGIS tool that will verify attributes, catch errors, and obtain user input to rectify those error. I want the tool to select and zoom to the segment that is being currently assessed so that they can make an informed decision. This is what I have been using, and it works well. But the CONVWGID is the variable that will be changing, and I'm not sure how to input that variable into an SQL statement without causing errors.

This is how I had tested the logic:

def selectzoom():
    arcpy.SelectLayerByAttribute_management(Convwks, "NEW_SELECTION", " [CONVWGID] = 10000001")

    mxd = arcpy.mapping.MapDocument('CURRENT')
    df = arcpy.mapping.ListDataFrames(mxd, "Layers") [0]
    df.zoomToSelectedFeatures()
    arcpy.RefreshActiveView()

Then I needed to work the variable into the function in order to accept different CONVWGID values, which gives me a Runtime/TypeError that I should have known would happen.

Runtime error - Traceback (most recent call last): - File "string", line 1, in module - TypeError: cannot concatenate 'str' and 'int' objects

def selectzoom(convwkgid):
    delimfield = '" [CONVWGID] = ' + convwkgid + ' "'
    arcpy.SelectLayerByAttribute_management(Convwks, "NEW_SELECTION", delimfield)

    mxd = arcpy.mapping.MapDocument('CURRENT')
    df = arcpy.mapping.ListDataFrames(mxd, "Layers") [0]
    df.zoomToSelectedFeatures()
    arcpy.RefreshActiveView()

And when I alter the delimfield line to change the integer into a string, it selects all of the attributes in the entire feature class. Not just the one that had been passed via the function call.

delimfield = '"[CONVWGID] = ' + str(convwkgid) + '"'

I'm not amazing with SQL and maybe I'm missing something basic with this statement, but I can't figure out why it won't work when I'm basically giving it the same information:

"[CONVWGID] = 10000001"
'"[CONVWGID] = ' + str(convwkgid) + '"'
4

It's maybe your extra double quotes at the beginning and end of your code:

Let's say convwkgid = 10000001

'"[CONVWGID] = ' + str(convwkgid) + '"' doesn't equal "[CONVWGID] = 10000001"

'"[CONVWGID] = ' + str(convwkgid) + '"' would actually be '"[CONVWGID] = 10000001"'

Try instead:

'[CONVWGID] = ' + str(convwkgid)

  • Hey @Emil Brundage, This was the fix I needed. I don't know why I didn't try to troubleshoot it like that. Thanks a lot for your help! – Ben Ference Jul 13 '15 at 19:00
  • Any time. Enjoy the pythoning. – Emil Brundage Jul 13 '15 at 19:01
  • As an aside the square brackets are not needed for SQL statements unless there's a join involved. '[CONVWGID] = ' + str(convwkgid) is the same as 'CONVWGID = ' + str(convwkgid). This simplifies the syntax some cases use "FIELD" where others use [FIELD] - neither matters so you don't need to test if it's a file/personal geodatabase, SDE, shapefile or CAD feature class before scripting your query. – Michael Stimson Jul 14 '15 at 2:40
  • @MichaelMiles-Stimson Hey, I actually never knew that before so thanks. I always thought that SQL statement syntax was very dependent on the file being processed/looked at, and just took whatever the query builder suggested to me. I'm gonna look into this more now! – Ben Ference Jul 14 '15 at 14:36
  • Delimiting the field is required in CalculateField_management, have a look at AddFieldDelimeters resources.arcgis.com/en/help/main/10.1/index.html#//… which takes a lot of hard work out. Another 'special' is the Mod function FIELD MOD 10 = 0 or mod(FIELD,10) = 0 depends on the database... the more advanced SQL definitely depends on the database being queried. – Michael Stimson Jul 14 '15 at 21:42
3

Let arcpy build the correct syntax for you and use .format() so you don't need to juggle extra quotes:

def selectzoom(convwkgid):
    fc = "Convwks"
    field = arcpy.AddFieldDelimiters(fc, "CONVWGID")
    selection = "{f} = {v}".format(f=field, v=convwkgid)

    arcpy.SelectLayerByAttribute_management(fc, "NEW_SELECTION", selection)

    mxd = arcpy.mapping.MapDocument('CURRENT')
    df = arcpy.mapping.ListDataFrames(mxd, "Layers") [0]
    df.zoomToSelectedFeatures()
    arcpy.RefreshActiveView()
  • This helped me to catch an error in my coding, and I never really utilize the .format function as often as I could. Thanks for the help, the reminder, and taking the time to answer! – Ben Ference Jul 14 '15 at 14:38
  • I didn't know the .format() method took keywords {f}, {v} in addition to indices {0}, {1}. Thanks! – John Jul 22 '15 at 23:06

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