UpdateCursor 'is not defined' Python

Question

I have several files (shapefiles). Table 1 has only one row with several fields whereas Table 2 has several rows. What I want is to take a value from Table 1 and populate all rows in Table 2. I used a SearchCursor to find the value I want and an UpdateCursor to populate the rows.

import arcpy
arcpy.env.workspace = "C:\\Users\\Documents\\Scoring\\Ecodis_clip_split" 
#set workspace to folder with values
rows = arcpy.SearchCursor ("Table1.shp", "", "", "area_ha", "") 
#search for the value in attributetable
arcpy.env.workspace = "C:\\Users\\Documents\\Scoring\\Split_wetlandt" 
#set workspace to folder with files which need to be updated
rows = UpdateCursor ("Table2.shp", "", "", "area_eco", "") 
#Update all rows of file with value from SearchCursor above

Running this, I keep getting this Errormessage:

Traceback (most recent call last):
File "<module1>", line 17, in <module>
NameError: name 'UpdateCursor' is not defined

If something is not defined, this means that Python sees it as a variable? Even if I could get rid of the errormessage: would it populate all the rows in Table 2 with the value or do I need to do something else? Note that I just started to learn Python and never scripted anything what so ever...

Edit 6/17/14 11:32 am

@ Aaron, would this replace the values in Table 2 with my searched values from table 1?

import arcpy
arcpy.env.workspace = "C:\\Users\\Documents\\Scoring\\Ecodis_clip_split" 
#set workspace to folder with values
rows = arcpy.SearchCursor (table 1", "", "", "area_ha", "") 
#search for the value in attributetable
arcpy.env.workspace = "C:\\Users\\Documents\\Scoring\\Split_wetlandt" 
#set workspace to folder with files which need to be updated
with arcpy.UpdateCursor (Table 2 ["area_eco"]) 
#Update all rows of file with value from SearchCursor above
for row in cursor:
 area_eco.replace(SearchCursor)

EDIT 6/27614 12:04pm

I updated my script to this. Somehow it deleted my whole attributetable in Table 2 but I got it restored. I run it again and now nothing happens. It does not update the rows, the value in the rows stays 0.

import arcpy
arcpy.env.workspace = "C:\\Users\\Documents\\Scoring\\Ecodis_clip_split" 
#set workspace to folder with values
rows = arcpy.SearchCursor ("Table1", "", "", "area_ha", "") 
#search for the value in attributetable
arcpy.env.workspace = "C:\\Users\\Documents\\Scoring\\Wetland" 
#set workspace to folder with files which need to be updated
rows = arcpy.UpdateCursor ("Table2", "", "", "area_ha", "")
del rows

• Paul: You forgot arcpy.UpdateCursor()

Answer 1

You forgot to specify the arcpy module when calling UpdateCursor.

 rows = arcpy.UpdateCursor ("Table2.shp", "", "", "area_eco", "")

I second Aaron regarding using the with statement

Also, I would reference one of my OS answer regarding using either the "classic" cursor or the data access (da) one.

Finally, I would like to point you to a few resources to help you learn python/arcpy:

• 10 Easy way to Tame Python
• Seven easy ways to start learning Python
• Esri Blog on Python
• Arcpy Café

Hope it helps.

• four-eyes: Updating this an trying to run the script, it bounces back with this RuntimeError: ERROR 999999: Error executing function. Cannot acquire a lock. Cannot acquire a lock.
• ericchiasson: Close ArcMap/ArcCatalog and other Python IDEs that you have open.
• four-eyes: Weeeell, something happend, but not what I wanted it to do. It deleted now my whole attributestable instead of updating it...
• ericchiasson: @Stophface I hope you have a backup...
• four-eyes: Sure I do :) Got it restored already. But where is the problem?!

Answer 2

What is going on here is that the Python interpreter does not know where "UpdateCursor" came from. The correct syntax is as follows (i.e. ArcGIS 10.1+):

arcpy.da.UpdateCursor(YourFeatureclass, ["Field1", "Field2", "Field3", "etc"])

A very clean way to implement a cursor is by using the with statement:

with arcpy.da.UpdateCursor(YourFeatureclass, ["Field1", "Field2", "Field3", "etc"]) as cursor:
 for row in cursor:
 # Do something 

Cursor objects are automatically opened, processed in some way and closed automatically using a with statement. More details are available on the ESRI help section on UpdateCursors.

• four-eyes: Hey. Thank you! I edited my post. I am not sure how I tell 'do something' to use the value of my search cursor
• Aaron: @Stophface I would recommend opening a new question to address that. My initial thought is to run a search cursor and populate a list and then use that list to update a the new table via the update cursor.
• four-eyes: Ah, alright. Well, I tried the script I wrote with the added arcpy and it deleted my attributetable the shapefile I wanted to update.

Answer 3

This is based on my understanding. I didn't test the script but this should work. Provide me a link to your data if you need further debugging.

import arcpy
arcpy.env.workspace = "C:\\Users\\Documents\\Scoring\\Ecodis_clip_split" 
#set workspace to folder with values
# Create a cursor for Ecodis
cursorEco = arcpy.SearchCursor ("Table1", "", "", "area_ha", "") 
#search for the value in attributetable
arcpy.env.workspace = "C:\\Users\\Documents\\Scoring\\Wetland" 
#set workspace to folder with files which need to be updated
# Create a cursor for Wetland
cursorWet = arcpy.UpdateCursor ("Table2", "", "", "area_ha", "")
# Itereate each row within the Ecodis cursor 
for rowEco in cursorEco:
 print(rowEco.getValue("area_ha"))
 # Itereate each row within the Wetland cursor
 for rowWet in cursorWet:
 # Assign the value of Ecodis row to the Wetland row
 rowWet.setValue("area_ha", rowEco.getValue("area_ha"))
 # Save the changed made to the Weltand
 cursorWet.updateRow(rowWet)
# Clean-up
if cursorEco: 
 del cursorEco
if cursorWet:
 del cursorWet
if rowEco:
 del rowEco
if rowWet:
 del rowWet

• four-eyes: Hey thanks a lot for your effort. SyntaxError: Cant assign to function call (<module3>, line 34) pops up highlighting this bit of code rowWet.setValue("area_ha") = rowEco.getValue("area_ha") I guess there is a mistake in the Syntax? I put already 4 spaces in there but that did not help.
• ericchiasson: @Stophface I've made a change. See how it works.
• Paul: It would likely be more efficient if you accessed the value of row.Eco only once. Also, you can use a try...except block for your deletions. Less lines and it handles exceptions with lock files better.
• four-eyes: Error executing function. The index passed was not within the valid range. Aaaand it delets all my rows in the attributetable where the value is supposed to go in again.
• four-eyes: Hey. I tried something different with a list and had some questions about that. The solution is here gis.stackexchange.com/questions/103515/… Thanks a lot for your effort :)