topic Re: Populate fields using python (cumulative) in Python Questions

Re: Populate fields using python (cumulative)

TerryGustafson — Wed, 14 Oct 2015 12:50:44 GMT

Ok I think I’m close but need a little more help. I have a
table like the one attached. I’m trying to create a line segment from it
that goes from 22.473 to 27.346 but they are on separate lines. I need a
python script to calculate the to_measure from OBJECTID 1 equal to the
to_measure from OBJECTID2. Do you think that is possible?

Re: Populate fields using python (cumulative)

JakeSkinner — Fri, 10 Dec 2021 22:14:18 GMT

You can iterate through each RID and update the to_MEAS field. Ex:

table = "Sample"

ridList = []

with arcpy.da.SearchCursor(table, ["RID"]) as cursor:
    for row in cursor:
        ridList.append(row[0])

del cursor

ridList = set(ridList)

for RID in ridList:
    toMeasList = []
    with arcpy.da.SearchCursor(table, ["RID", "to_MEAS"], "RID = '" + RID + "' ") as cursor:
        for row in cursor:
            toMeasList.append(row[1])
    del cursor
    toMeasList.sort()

    with arcpy.da.UpdateCursor(table, ["to_MEAS"], "RID = '" + RID + "'") as cursor:
        for row in cursor:
            row[0] = toMeasList[-1]
            cursor.updateRow(row)
    del cursor

Re: Populate fields using python (cumulative)

TerryGustafson — Wed, 14 Oct 2015 13:49:34 GMT

I get a 000539 : Error message from Python. It seems like it should work. At the end its taking the row[0] array and setting the toMeasList equal to it minus 1 record correct?

Re: Populate fields using python (cumulative)

TerryGustafson — Wed, 14 Oct 2015 14:13:35 GMT

Says syntax error line 1 which is declaring the table correct?

Re: Populate fields using python (cumulative)

JakeSkinner — Wed, 14 Oct 2015 14:24:11 GMT

Yes, you will need to update the 'table' variable with the feature class/table in the Table of Contents. Ex:

table = 'RoutingTable'

Re: Populate fields using python (cumulative)

TerryGustafson — Wed, 14 Oct 2015 14:25:43 GMT

I did that, the table is called result. Does it have to be a certain type of table?

Re: Populate fields using python (cumulative)

JakeSkinner — Wed, 14 Oct 2015 14:28:20 GMT

Can you zip and upload the table you are using?

Re: Populate fields using python (cumulative)

TerryGustafson — Fri, 10 Dec 2021 22:14:21 GMT

I created sever types of table and set the table variable but seems to keep throwing the syntax at line 1. Here is an example of an exported table and the code I used.

table = "Export_Output"
ridList = []
with arcpy.da.SearchCursor(table, ["RID"]) as cursor:
    for row in cursor:
        ridList.append(row[0])
del cursor
ridList = set(ridList)
for RID in ridList:
    toMeasList = []
    with arcpy.da.SearchCursor(table, ["RID", "to_MEAS"], "RID = '" + RID + "'") as cursor:
        for row in cursor:
            toMeasList.append(row[1])
    del cursor
    toMeasList.sort()
    with arcpy.da.UpdateCursor(table, ["to_MEAS"], "RID = '" + RID + "'") as cursor:
        for row in cursor:
            row[0] = toMeasList[-1]
            cursor.updateRow(row)
    del cursor

Re: Populate fields using python (cumulative)

TerryGustafson — Wed, 14 Oct 2015 17:07:31 GMT

Ok, made a little headway. It appears to not like the null values in the fields. When I: replace them with 0 then it does not error out at line 1 anymore. :It then give me the warming. "A Field name was not found or there were unbalanced quotation marks". I was not sure if this was due to line 21 or 15..

Re: Populate fields using python (cumulative)

TerryGustafson — Wed, 14 Oct 2015 21:25:24 GMT

This is an image of the errors I receive in ArcMap

Re: Populate fields using python (cumulative)

DarrenWiens2 — Wed, 14 Oct 2015 21:43:03 GMT

I'm jumping into this thread midstream, but I'm confused why this has anything to do with Calculate Field. You're running this in the Python window, not the field calculator, correct?

In any case, it looks like however you are calling CalculateField, it is set to VB not Python.

Re: Populate fields using python (cumulative)

TerryGustafson — Wed, 14 Oct 2015 21:47:12 GMT

I’m trying to calculate a field based on another field in a table using python in the field Calculator.

Re: Populate fields using python (cumulative)

DarrenWiens2 — Wed, 14 Oct 2015 21:54:10 GMT

The last line in the error message indicates that the Field Calculator was run in VB mode:

del cursor" VB #

Re: Populate fields using python (cumulative)

TerryGustafson — Wed, 14 Oct 2015 21:58:36 GMT

That is my fault I copied the wrong results.. I get an invalid syntax when I select python..

Re: Populate fields using python (cumulative)

DarrenWiens2 — Wed, 14 Oct 2015 22:04:29 GMT

Not sure if it's an error in the error message or your code, but the line ridList.append(row[0]) should be indented twice.

edit: actually, there are several indentation errors, probably just a problem in the error message. Can you post your code so we can see your indentation? Instructions here.

Re: Populate fields using python (cumulative)

JakeSkinner — Thu, 15 Oct 2015 12:04:25 GMT

Terry,

The code I provided was written to be run in the python window. Attached is an example. Here are the steps to take:

1. Add the 'sample' table to ArcMap

2. Open the Python window

3. Open 'script1.py' in a text editor

4. Copy the syntax

5. Paste into the Python window and click Enter a couple of times to execute the code

The 'sample' table should be updated successfully.

Re: Populate fields using python (cumulative)

TerryGustafson — Thu, 15 Oct 2015 12:28:37 GMT

Ok, that does work, I was trying to run the python code via the Field calculator. Is that possible? The reason I wanted to do that was I’m building a model to run a process and the second to the last step is to populate the to_MEAS so I can create a line segment.

Re: Populate fields using python (cumulative)

JakeSkinner — Thu, 15 Oct 2015 12:56:55 GMT

It may be easier to add the script to the model. The only thing you would need to change in the script is the 'table' variable. You would need to set this to the full path to where the table is. Ex:

table = r"C:\data\sample.dbf"

Re: Populate fields using python (cumulative)

TerryGustafson — Thu, 15 Oct 2015 13:16:01 GMT

Ok, I’m stuck on what my parameters should be for the “Display Name” and “Data Type”. I’m thinking Display name is “RID” and Data type is numeric? Also the table is actually going to be in memory so will I need to set the table path?

Re: Populate fields using python (cumulative)

JakeSkinner — Thu, 15 Oct 2015 13:38:58 GMT

You actually won't need to set any parameters. This is only necessary if the python code contains 'arcpy.GetParameterAsText'. However, I believe you are going to have to export the table from IN MEMORY to disk. Then you can update the script to this path.