topic Re: SearchCursor, create unique lists, convert to dictionary in Python Questions

SearchCursor, create unique lists, convert to dictionary

MatthewRusso — Sun, 12 Dec 2021 04:01:54 GMT

fc = 'Texas'
field1 = "COUNTY_CODE"
field2 = "NAME10" 
list1 = []   
list2 = [] 
rows = arcpy.SearchCursor(fc)

for row in rows:
    list1.append(row.getValue(field1))
    list2.append(row.getValue(field2))
else:
    print "loop failed"

#Get Unique Values from the List         
uSet1 = set(list1)
uSet2 = set(list2)

#Convert the set to a list
uList1 = list(uSet1)
uList2 = list(uSet2)

#Print The list
print uList1
print uList2

#Create Dictionary from the 2 lists and print results
from itertools import chain, repeat
d = dict(zip(uList1, chain(uList2, repeat(None))))

for key,val in d.items():
    print key,val

Re: SearchCursor, create unique lists, convert to dictionary

MatthewRusso — Thu, 05 Feb 2015 17:15:47 GMT

Don't know what happened but i can't find the post editor.

Basically I am getting an error:

Runtime error

Traceback (most recent call last):

File "<string>", line 12, in <module>

File "c:\program files (x86)\arcgis\desktop10.1\arcpy\arcpy\arcobjects\arcobjects.py", line 1044, in getValue

return convertArcObjectToPythonObject(self._arc_object.GetValue(*gp_fixargs(args)))

RuntimeError: ERROR 999999: Error executing function.

I am trying to create 2 list via the search cursor, then put them in a dictionary. I might be doing this completely wrong but what I am doing makes sense to me. I can run through the first list no problem, but get an error when i add the second list.

Any help would be awesome.

Re: SearchCursor, create unique lists, convert to dictionary

BlakeTerhune — Thu, 05 Feb 2015 17:22:51 GMT

Post manage options (edit and delete) are under the Actions menu at the extreme bottom left of each post.

Re: SearchCursor, create unique lists, convert to dictionary

MatthewRusso — Thu, 05 Feb 2015 17:25:08 GMT

It's showing up for my reply but not the main post

Re: SearchCursor, create unique lists, convert to dictionary

XanderBakker — Sun, 12 Dec 2021 04:01:56 GMT

The error probably refers to the problem obtaining a value using getValue. You may check the name of the field (does it exist) and the content of the field (empty values?).

Are you using 10.0? If you have access to 10.1 (SP1) you can use the data access module that makes life a lot easier:

To create a dictionary from OID and an arbitrary field:

fc = r'C:\path\to\your\featureclass\or\table' 
fld_oid = arcpy.Describe(fc).OIDfieldname 
fld_other = 'afieldname' 
d = {r[0]: r[1] for r in arcpy.da.SearchCursor(fc, (fld_oid, fld_other))}

What should the dictionary contain?

Some more info and useful snippets can be found here: Some Python Snippets

Re: SearchCursor, create unique lists, convert to dictionary

MatthewRusso — Thu, 05 Feb 2015 17:37:54 GMT

Dictionary should contain the County ID/County Name to be used later to run through an extraction process.

I am on 10.1 SP1 Adv Copy

fc = "Texas" is a fc in a geodatabase

I am pulling parcel data out of 10 states so i want to pull the info out of the tables for my selection process and naming convention. I have to do this on a weekly basis coming up so I am trying to have a script to run overnight.

The parcel file is joined to another file, could this effect it?

Re: SearchCursor, create unique lists, convert to dictionary

BlakeTerhune — Thu, 05 Feb 2015 17:41:14 GMT

Does using a search cursor in a list (dictionary) comprehension like this automatically close the cursor when it's finished like when using it in a with block?

EDIT:

I did a quick test and it looks like the lock does go away. Spiffy!

Re: SearchCursor, create unique lists, convert to dictionary

XanderBakker — Sun, 12 Dec 2021 04:01:59 GMT

Try this and see if it works:

import arcpy
# set your workspace
# (or not if you run this in the Python Window and the layer Texas is in your TOC)
# arcpyy.env.workspace = r"drive:\path\to\your\input\fgdb.gdb" # or folder

fc = 'Texas'
field1 = "COUNTY_CODE"
field2 = "NAME10"

# create dictionary
d = {r[0]: r[1] for r in arcpy.da.SearchCursor(fc, (field1, field2))}

for key,val in d.items():
    print key,val

Re: SearchCursor, create unique lists, convert to dictionary

BlakeTerhune — Thu, 05 Feb 2015 17:53:37 GMT

Ah, yes, forgot about that. The actions for the original post are at the top of the post off to the right (under the following, share, bookmark, and like options).

Re: SearchCursor, create unique lists, convert to dictionary

MatthewRusso — Sun, 12 Dec 2021 04:02:02 GMT

So i'm testing the da.searchcursor right now, i believe there is some issue with joining the 2 Feature class tables.

my first test i ran with 1 of my fields the "COUNTY_CODE" and it worked, created a unique list fine

I then joined my files and ran the exact same script and it said "Cannot find field 'COUNTY_CODE'"

I am trying to export to a new file to see if the join was acting like a temp file or something, kind of strange.

Here is where I am at. I don't want to make it a dictionary right of the bat so i can test it vs. all the states.

fc = 'Texas2'
field1 = "COUNTY_CODE"
field2 = "NAME10" 

list1 = [row[0] for row in arcpy.da.SearchCursor(fc, field1)]
list2 = [row[0] for row in arcpy.da.SearchCursor(fc, field2)]

#Get Unique Values
uValue1 = set(list1)
uValue2 = set(list2)
#Convert to a List
uList1 = list(uValue1)
uList2 = list(uValue2)

print(uValue1)
print(uValue2)

#Create Dictionary from the 2 lists and print results
from itertools import chain, repeat
d = dict(zip(uList1, chain(uList2, repeat(None))))

for key,val in d.items():
    print key,val

Re: SearchCursor, create unique lists, convert to dictionary

BlakeTerhune — Sun, 12 Dec 2021 04:02:04 GMT

Maybe you have to call your field name as "featureclass.fieldname" beacuse that's how ArcMap renames when you join. Try using ListFields to print the name of the fields on the feature class you're running the SearchCursor on (Texas2) so you can see what you're working with.

fields = arcpy.ListFields(fc)
for f in fields:
    print f.name

EDIT:

Are you doing the join in Python?

ArcGIS Help 10.1 - Add Join (Data Management)

Re: SearchCursor, create unique lists, convert to dictionary

MatthewRusso — Thu, 05 Feb 2015 18:53:58 GMT

EDIT: I have joined it via GP Tool

Ok, progress has been made. I ran what you listed above and it looks like my fields are showing up as seperate files still(guessing because of the Join)

I tried to make the join permenate by exporting/copying feature but it isn't working since the fields are still linking to the joined file.

Notice the print of f.name

#Texas FC

Texas_COUNTY_CODE

Texas_STATE_CODE

#Texas_Counties FC

Texas_Counties_FID

Texas_Counties_STATEFP10

Texas_Counties_COUNTYFP10

Texas_Counties_NAME10

It seems like it is working, just can't find that field because it is not displaying as the "Texas" FC

Re: SearchCursor, create unique lists, convert to dictionary

BlakeTerhune — Thu, 05 Feb 2015 19:02:27 GMT

Try doing the join in Python using arcpy.AddJoin_management() (see example 2 at the bottom). Once you've done the join, then print the field names and see what you need to use for the search cursor.

Re: SearchCursor, create unique lists, convert to dictionary

BlakeTerhune — Thu, 05 Feb 2015 20:45:26 GMT

After further investigation, I should clarify that the feature class needs to be a feature layer before you can do the join. Once you do the join, the field names on the feature layer are indeed "featureclassname.fieldname".