topic Re: Creating a Function with an Update Cursor in Python Questions

Creating a Function with an Update Cursor

JamesMcAllister1 — Thu, 08 Apr 2021 21:52:54 GMT

I have an update cursor that updates rows of a feature class on AGOL. The code below works.

with arcpy.da.UpdateCursor (fc, ['OBJECTID_1', 'Wk4_March29April1_ACTIV','Wk4_HRS', 'Wk5_April5April8_ACTIV','Wk5_HRS'], "Wk4_March29April1_ACTIV LIKE '%Planned%'") as cursor: for row in cursor: row[3] = row[1] row[4] = row[2] row[1] = None row[2] = None cursor.updateRow(row)

I'm now trying to turn this code into a function so I don't have to keep hard coding the values. However, the function I've made isn't working when I call it and pass in the variables I want to use. The code below is the function.

def weekly_update(week_a, hours_a, week_b, hours_b): with arcpy.da.UpdateCursor (fc, ['OBJECTID_1', 'week_a','hours_a', 'week_b','hours_b'], "week_a LIKE '%Planned%'") as cursor: for row in cursor: row[3] = row[1] row[4] = row[2] row[1] = None row[2] = None cursor.updateRow(row) #call the function and pass in the variables weekly_update("Wk25_Oct12Oct15_ACTIV", "Wk25_HRS", "Wk26_Oct19Oct22_ACTIV", "Wk26_HRS")

This is the error I keep getting

RuntimeError: A column was specified that does not exist. [week_a]

Any suggestions would be great. Thanks!

Re: Creating a Function with an Update Cursor

JoeBorgione — Thu, 08 Apr 2021 22:25:28 GMT

def weekly_update(week_a, hours_a, week_b, hours_b): with arcpy.da.UpdateCursor (fc, ['OBJECTID_1', 'week_a','hours_a', 'week_b','hours_b']

Try removing the quotes around your parameter-variable names. When you enclose them like that the cursor is looking for a field of those names instead of the value of the variables.

Re: Creating a Function with an Update Cursor

JamesMcAllister1 — Thu, 08 Apr 2021 22:46:27 GMT

Unfortunately, that doesn't work.

Re: Creating a Function with an Update Cursor

Anonymous User — Thu, 08 Apr 2021 23:26:20 GMT

Joe is correct. ...An alternative that might help keep variables and parameter assignments from getting tangled is to just pass a list of the fields like:

fldList = ["Wk25_Oct12Oct15_ACTIV", "Wk25_HRS", "Wk26_Oct19Oct22_ACTIV", "Wk26_HRS"] def weekly_update(fldList): with arcpy.da.UpdateCursor (fc, fldList, "{} LIKE '%Planned%'".format(fldList[0])) as cursor: for row in cursor: row[3] = row[1] row[4] = row[2] row[1] = None row[2] = None cursor.updateRow(row) #call the function and pass in the variables weekly_update(fldList)

Re: Creating a Function with an Update Cursor

RandyBurton — Thu, 08 Apr 2021 23:02:36 GMT

@JoeBorgioneand @Anonymous User offer good solutions. But you also need to use the proper form in your query since 'week_a' is a variable name and not the actual field name.

def weekly_update(week_a, hours_a, week_b, hours_b): with arcpy.da.UpdateCursor (fc, ['OBJECTID_1', week_a,hours_a, week_b,hours_b], "{} LIKE '%Planned%'".format(week_a)) as cursor:

Or, with Jeff's idea:

Re: Creating a Function with an Update Cursor

JoeBorgione — Thu, 08 Apr 2021 22:58:10 GMT

(fc, ['OBJECTID_1', week_a, hours_a, week_b, hours_b], "week_a LIKE '%Planned%'")

Then it must be the reference to week_a in your selection statement that's bombing it. (I didn't notice that).

If you are using python 3.x I suggest using an f string like this:

(fc, ['OBJECTID_1', week_a, hours_a, week_b, hours_b], f'{week_a} LIKE "%Planned%"')

of if you are using python 2.x you'll need to use the format() method:

(fc, ['OBJECTID_1', week_a, hours_a, week_b, hours_b], '{} LIKE "%Planned%"'.format(week_a)

(Of course these are untested, but I think that'll get you going...)

Re: Creating a Function with an Update Cursor

BlakeTerhune — Thu, 08 Apr 2021 23:01:31 GMT

This is a good solution. Just be aware @JamesMcAllister1 that if you don't pass the right number of fields, the field assignment will error out. You could validate the fldList argument before opening the cursor to make sure it's got four items.

assert len(fldList) == 4, "fldList must have exactly 4 field names; like week_a, hours_a, week_b, hours_b"

Re: Creating a Function with an Update Cursor

JamesMcAllister1 — Thu, 08 Apr 2021 23:21:22 GMT

Thank you, I like the idea of using a list and having an assert statement.

Re: Creating a Function with an Update Cursor

JamesMcAllister1 — Thu, 08 Apr 2021 23:22:59 GMT

Thank you, the .format() is exactly what I needed.

"{} LIKE '%Planned%'".format(fldList[0])