topic Re: How to Extract values from a field and write them to a text file using Python? in Python Questions

How to Extract values from a field and write them to a text file using Python?

ChristiNelson1 — Thu, 11 Jul 2013 17:06:38 GMT

Hi all,

I am using ArcGIS 10.0 Python 2.6. I need to get the values from a single field (APN) out of a PARCEL feature class attribute table and write them to a text file. The feature class contains about 20 different fields. I only need to write the values from APN.

The only info I can find is outdated. Can anyone help?

Thanks,
Christi Nelson

Re: How to Extract values from a field and write them to a text file using Python?

Anonymous User — Sat, 11 Dec 2021 18:24:40 GMT

This is untested but I think it should do the trick.

import arcpy

def WriteFieldToText(table, field, text_file):

    # Open search cursor to loop thru table
    rows = arcpy.SearchCursor(table)
    f = open(text_file, 'w')
    for row in rows:
        f.write(str(row.getValue(field)) + '\n')
    del row, rows
    f.close()
    print 'Created "%s"' %text_file
    

if __name__ == '__main__':

    fc = r'C:\Path\To_your\featureClass'
    field = 'APN'
    output = r'C:\Path\To_your\textfile.txt'

    # run function
    WriteFieldToText(fc, field, output)

Re: How to Extract values from a field and write them to a text file using Python?

PhilMorefield — Thu, 11 Jul 2013 17:56:41 GMT

This is very easily done. You can read a little about SearchCursors here, and about writing to text files with Python here (page down to section 7.2 Reading and Writing Files.

The general pattern for this operation in AGD 10.0 is something like this:

import arcpy as ap  # this is how you create a file in Python myOutputFile = open('C:\\temp\\myoutputfile.txt', 'w')  # create a row object to navigate your table rows = ap.SearchCursor('C:\\temp\\myInputTable.shp') row = rows.next()  # for each row in your table, retrieve the value in the 'APN' field, convert it # to a string, write it to your output file, then move to the next line in both # your input table and output file for row in rows:     myOutputFile.write(str(row.APN) + '\n')  del row, rows myOutputFile.close()

Re: How to Extract values from a field and write them to a text file using Python?

T__WayneWhitley — Thu, 11 Jul 2013 17:57:03 GMT

More than one way to do this, but I suppose the easiest (not necessarily the most efficient) is to use:

Export Feature Attribute to ASCII (Spatial Statistics)
Resource Center » Professional Library » Geoprocessing » Geoprocessing tool reference » Spatial Statistics toolbox » Utilities toolset
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//005p0000003v000000

...also, the input can be a feature layer, meaning if you wanted you should be able to 'pare down' the output fields with the field info control. This is available with the Make Feature Layer tool -- an example of how to use the field info control in a script is with the webhelp on Make Table View, so if you need that, it's here (and it should be used the same way with Make Feature Layer):

Make Table View (Data Management)
Resource Center » Professional Library » Geoprocessing » Geoprocessing tool reference » Data Management toolbox » Layers and Table Views toolset
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//00170000006v000000

Enjoy,
Wayne

Edit: It's even easier than that! You don't need Make Feature Layer, you can specify what you wish in the 2nd param (Value_Field) of the Spatial Statistics tool. One tool! (if you don't mind the additional XY coords)

Re: How to Extract values from a field and write them to a text file using Python?

ChristiNelson1 — Sat, 11 Dec 2021 18:24:43 GMT

This is very easily done. You can read a little about SearchCursors here, and about writing to text files with Python here (page down to section 7.2 Reading and Writing Files.

The general pattern for this operation in AGD 10.0 is something like this:
import arcpy as ap

# this is how you create a file in Python
myOutputFile = open('C:\\temp\\myoutputfile.txt', 'w')

# create a row object to navigate your table
rows = ap.SearchCursor('C:\\temp\\myInputTable.shp')
row = rows.next()

# for each row in your table, retrieve the value in the 'APN' field, convert it
# to a string, write it to your output file, then move to the next line in both
# your input table and output file
for row in rows:
    myOutputFile.write(str(row.APN) + '\n')

del row, rows
myOutputFile.close()

Thank you!

This worked seamlessly. Funny, I did read section 7.2 in the text you provided, but hit a road block trying to incorporate it with a search cursor.

Thanks for all of your help, everyone!
Christi

Re: How to Extract values from a field and write them to a text file using Python?

ChrisSnyder — Sat, 11 Dec 2021 18:24:46 GMT

The .next() statement (in addition to the for loop) is unneccessary. I think a bit cleaner code would look like:

import arcpy
myOutputFile = open('C:\\temp\\myoutputfile.txt', 'w')
rows = ap.SearchCursor('C:\\temp\\myInputTable.shp')
for row in rows:
    myOutputFile.write(str(row.APN) + '\n')
del row, rows
myOutputFile.close()

Also, in v10.1 syntax using the .da cursors (~30x faster than the old search cursors):

import arcpy
myOutputFile = open('C:\\temp\\myoutputfile.txt', 'w')
rows = arcpy.da.SearchCursor('C:\\temp\\myInputTable.shp',["APN"])
for row in rows:
    myOutputFile.write(str(row[0]) + '\n')
del row, rows
myOutputFile.close()

Re: How to Extract values from a field and write them to a text file using Python?

T__WayneWhitley — Thu, 11 Jul 2013 19:14:26 GMT

Christi, I had to give a point each to Caleb and Phil just because I thought it was neat to be able to compare the answers side by side --- both are good works!

If you like Phil's work best, you probably ought to give him the 'green checkmark' - he deserves it.

Enjoy,
Wayne

PS - And a point to Chris for being so efficient.... I was wondering why noone mentioned the da (data access) module. 30x faster is impressive!

Re: How to Extract values from a field and write them to a text file using Python?

ChristiNelson1 — Thu, 11 Jul 2013 19:25:02 GMT

Christi, I had to give a point each to Caleb and Phil just because I thought it was neat to be able to compare the answers side by side --- both are good works!

If you like Phil's work best, you probably ought to give him the 'green checkmark' - he deserves it.

Enjoy,
Wayne

PS - And a point to Chris for being so efficient.... I was wondering why noone mentioned the da (data access) module. 30x faster is impressive!

Done! Both answers were terrific.

Re: How to Extract values from a field and write them to a text file using Python?

Anonymous User — Sat, 11 Dec 2021 18:24:48 GMT

Just for fun, while talking about efficiency, may as well make to as few lines as possible 🙂

import arcpy
fc = r'G:\Data\Geodatabase\Cedar_County.gdb\CADASTRAL\PARCEL'
output = r'C:\Users\GIS\Desktop\textfile.txt'

with open(output, 'w') as f:
    f.write('\n'.join(r.PID for r in arcpy.SearchCursor(fc)))
print 'Created "%s"' %output

@ Wayne, I didn't mention the da module because she mentioned she was on version 10.0 still...but as Chris said, the new .da cursors are waaaay faster!

P.S. I need to limit my sugar intake while at work, feeling loopy...Happy scripting!

Re: How to Extract values from a field and write them to a text file using Python?

RhettZufelt — Thu, 11 Jul 2013 20:27:52 GMT

For comparison. run multiple times

>>>
took 5.42300009727 seconds to run using cursors
took 14.9790000916 seconds to run using Export_stats
took 1.01900005341 seconds to run using da.searchcursor
>>> ================================ RESTART ================================
>>>
took 5.4279999733 seconds to run using cursors
took 15.0590000153 seconds to run using Export_stats
took 1.11499977112 seconds to run using da.searchcursor
>>> ================================ RESTART ================================
>>>
took 6.02999997139 seconds to run using cursors
took 15.8759999275 seconds to run using Export_stats
took 1.08899998665 seconds to run using da.searchcursor
>>> ================================ RESTART ================================
>>>
took 5.89599990845 seconds to run using cursors
took 15.3450000286 seconds to run using Export_stats
took 1.04600000381 seconds to run using da.searchcursor
>>> ================================ RESTART ================================
>>>
took 6.25199985504 seconds to run using cursors
took 15.6540000439 seconds to run using Export_stats
took 1.0609998703 seconds to run using da.searchcursor
>>>

I find it interesting that using a single tool take so much longer...

R_

Re: How to Extract values from a field and write them to a text file using Python?

T__WayneWhitley — Thu, 11 Jul 2013 20:49:51 GMT

@Caleb, that's awesome! ...and oh yeah, v10.

@Rhett, good to know!! Interesting indeed, figured it would take longer, but that's much slower than I assumed. Nice comparison!

Enjoy,
Wayne

Re: How to Extract values from a field and write them to a text file using Python?

StacyRendall1 — Sat, 11 Dec 2021 18:24:51 GMT

Just for fun, while talking about efficiency, may as well make to as few lines as possible 🙂
import arcpy
fc = r'G:\Data\Geodatabase\Cedar_County.gdb\CADASTRAL\PARCEL'
output = r'C:\Users\GIS\Desktop\textfile.txt'

with open(output, 'w') as f:
    f.write('\n'.join(r.PID for r in arcpy.SearchCursor(fc)))
print 'Created "%s"' %output
@ Wayne, I didn't mention the da module because she mentioned she was on version 10.0 still...but as Chris said, the new .da cursors are waaaay faster!

P.S. I need to limit my sugar intake while at work, feeling loopy...Happy scripting!

If only I could +10 you for using join()!

Re: How to Extract values from a field and write them to a text file using Python?

RhettZufelt — Thu, 11 Jul 2013 23:53:47 GMT

If only I could +10 you for using join()!

Well, I can only give you one for it, but done....

R_