topic Re: Creating buffer with Python in Python Questions

Creating buffer with Python

ToddHowell — Wed, 09 Apr 2014 15:09:26 GMT

I am very new to python, and am trying to utilize a stand alone script that I can use on a working geodatabase full of feature classes in various feature datasets. Here's what I'm trying to accomplish, and the script that I have constructed.

1. I have a file geodatabase full of feature datasets based on county, inside of the county feature datasets I have feature classes that represent the center of aerial photography flight lines. These feature classes have a field that contains the flight height of the photography.

2. I have constructed a script that so far is unsuccessful at what I want it to accomplish. My goal is to have a script that will batch process all of the feature classes in the geodatabase, will create buffers of the lines contained in those feature classes based on the flight height field which needs to be multiplied by a factor of 1.502167099846. Then output into my separate geodatabase that will contain those photo coverages for use with an ArcGIS online map service.

Here is the script that I have constructed thus far:

 # Name: Flight_Line_Buffer.py # Description: Creates area of Aerial Photography coverage based on digitized flight lines, and associated flight height field in flight line table.  #Import system modules import arcpy from arcpy import env  # Set environment settings env.workspace = "J:\Flight_Lines_GDB\Flight_Lines_Coverage.gdb" env.Outworkspace = "J:\Aerial_Photo_GDB\Aerial_Photography_Coverage.gdb"  # Create buffer distance output from Flight Height field, and buffer flight lines Flightlines = "J:\Flight_Lines_GDB\Flight_Lines_Coverages.gdb" PhotoCoverages = "J:\Aerial_Photo_GDB\Aerial_Photography_Coverage.gdb" distanceField = "Flight_Height" sideType = "FULL" endType = "FLAT" dissolveType = "NONE" arcpy.Buffer_analysis(Flightlines, PhotoCoverages, distanceField, sideType, endType, dissolveType)

Things I know.
- I cannot just input the geodatabase as an input in the buffer tool, but I am unsure how to accomplish a loop or the like to process through all of the feature classes in the geodatabase.
-I cannot multiply a the field that I want to input as the buffer distance by a number either when I am defining it or in the tool parameters.
-I am a bit in over my head, and I am very very thankful for anyone with the patience and gracious nature to help me in any way.

Thanks for looking at this, I appreciate any help you can give.

Todd Howell

Re: Creating buffer with Python

Zeke — Wed, 09 Apr 2014 15:30:38 GMT

You need to loop through the features, creating a buffer for each one. As you access each one, you can multiply the value in the height field by your number. I doubt that you need or will see a better result by using a number with such precision, but hey, that's your call. You could use a search cursor to iterate through the records.

If you have a relatively small number of unique heights, it might be faster to select sets of features by height and buffer all of them with that value at once.

Re: Creating buffer with Python

ToddHowell — Wed, 09 Apr 2014 16:18:49 GMT

Thanks Greg! I appreciate the feedback. How exactly do I establish the geodatabase as a list for input into a for loop? Is there any way to preserve the feature datasets so that they transfer into the output geodatabase once the feature classes are processed through the buffer tool?

Re: Creating buffer with Python

IanMurray — Sat, 11 Dec 2021 21:46:51 GMT

From reading your post, I gather you have multiple feature datasets in your geodatabase with multiple feature classes in each, so you need to iterate through each dataset and feature class within the each dataset.

Easiest way to do that is to use arcpy.ListDatasets and arcpy.ListFeatureClasses

As for the multiplying the flight height field by your float value I'd use arcpy.SearchCursor to get the value from the field

# Name: Flight_Line_Buffer.py
# Description: Creates area of Aerial Photography coverage based on digitized flight lines, and associated flight height field in flight line table.

#Import system modules
import arcpy
from arcpy import env

# Set environment settings
env.workspace = "J:\Flight_Lines_GDB\Flight_Lines_Coverage.gdb"
env.Outworkspace = "J:\Aerial_Photo_GDB\Aerial_Photography_Coverage.gdb"

# Create buffer distance output from Flight Height field, and buffer flight lines
PhotoCoverages = "J:\Aerial_Photo_GDB\Aerial_Photography_Coverage.gdb"

#fetches all feaure datasets in workspace into a list
fdlist = arcpy.ListDatasets()

# loop through feature datasets in the list
for fd in fdlist:
     #setting new workspace to the feature dataset we are using
     env.workspace = fd 

     # fetches all feature classes in workspace into a list
     fclist = arcpy.ListFeatureClasses()

     #loop through feature classes in our list
     for fc in fclist:
          distanceField = "Flight_Height"
          sideType = "FULL"
          endType = "FLAT"
          dissolveType = "NONE"
          multiplier = 1.502167099846
          cursor = arcpy.SearchCursor(fc)
          for row in cursor:
                distance = ((row.getValue(distanceField))*(multiplier))
                arcpy.Buffer_analysis(fc, PhotoCoverages, distance, sideType, endType, dissolveType)

del row 
del cursor

Note this will only work for if there is only a single record in each feature class(which I am assuming from the fact you have multiple feature datasets and feature classes). The for loop for the cursor is not needed but I wasn't sure how to call it otherwise, I'm use to looping through multiple records at the same time.

Edit: I originally had arcpy.ListFeatureDatasets the correct syntax is arcpy.ListDatasets, sorry for the confusion

Re: Creating buffer with Python

IanMurray — Wed, 09 Apr 2014 16:47:41 GMT

You can use Copy_management tool to copy the feature datasets to your other geodatabase. Also if you wanted to save the feature classes in each feature dataset, then your output location would have to be the feature dataset in the output geodatabase, right now my code has it outputting as a feature class within the geodatabase.

Alternatively to using the cursor, you could just make a field in each feature classes that was the flight height multiplied by the float value you are using, then just use that field value as the value for the buffer, so you are using the field name as input instead of a number.

Re: Creating buffer with Python

Zeke — Wed, 09 Apr 2014 18:04:01 GMT

Alternatively to using the cursor, you could just make a field in each feature classes that was the flight height multiplied by the float value you are using, then just use that field value as the value for the buffer, so you are using the field name as input instead of a number.

Oh, sure, if you want to do it the easy way! 🙂

You could still use the looping concept to add and calculate the new field to each feature class.

Re: Creating buffer with Python

ToddHowell — Thu, 10 Apr 2014 12:51:46 GMT

Ian,
WOW. Thanks for the help, I do have feature classes with multiple records. Is it possible to work with that same code and modify it to work? The reason I have multiple datasets and feature classes is I am working with statewide data, and needed to be able to apply the state plane coordinates to each different area based on county, and then have feature classes based on towns. However, some towns have multiple flight lines so they required multiple records in the feature class.

Currently I am working mostly with the ESRI Press Python Scripting for ArcGIS book. Are there any other resources you could recommend for a person new to programming to get a good start with. I need to preserve the feature datasets into the new geodatabase as well. How would that best fit into the script example you have given?

Thanks again for your help, I'm really taken aback at how helpful the Python community as a whole is.

Todd Howell

Re: Creating buffer with Python

ToddHowell — Thu, 10 Apr 2014 13:04:56 GMT

Runtime error
Traceback (most recent call last):
File "<string>", line 35, in <module>
File "c:\program files (x86)\arcgis\desktop10.2\arcpy\arcpy\arcobjects\arcobjects.py", line 1064, in getValue
return convertArcObjectToPythonObject(self._arc_object.GetValue(*gp_fixargs(args)))
RuntimeError: ERROR 999999: Error executing function.

I'm having trouble figuring out why it is returning this error when I try to run that code in ArcGIS as well.

Re: Creating buffer with Python

IanMurray — Thu, 10 Apr 2014 16:44:40 GMT

Ian,
WOW. Thanks for the help, I do have feature classes with multiple records. Is it possible to work with that same code and modify it to work? The reason I have multiple datasets and feature classes is I am working with statewide data, and needed to be able to apply the state plane coordinates to each different area based on county, and then have feature classes based on towns. However, some towns have multiple flight lines so they required multiple records in the feature class.

Currently I am working mostly with the ESRI Press Python Scripting for ArcGIS book. Are there any other resources you could recommend for a person new to programming to get a good start with. I need to preserve the feature datasets into the new geodatabase as well. How would that best fit into the script example you have given?

Thanks again for your help, I'm really taken aback at how helpful the Python community as a whole is.

Todd Howell

You can you the copy the feature datasets with arcpy.Copy_management, which can be put in the python script, probably while you are looping through feature datasets.
THis is one problem
arcpy.Buffer_analysis(fc, PhotoCoverages, distance, sideType, endType, dissolveType)
as it needs to output to a feature class, which we have it outputting to a geodatabase, but its a pretty easy fix, but we need to make sure it has a different output name each time or it will crash.

Busy at work right now, but I can help you out again in a bit. I'm pretty new to python myself, so not familiar with alot of good online resources, but arcgis help within ArcGIS is really handy for checking syntax and what your input and outputs for the methods are.

Re: Creating buffer with Python

Zeke — Thu, 10 Apr 2014 18:01:28 GMT

You might want to set your distance_height through multiplier variables outside of the for loop to save the overhead of setting them each trip through the loop. Might only be a negligible performance hit, but good practice to avoid it if not needed.

Re: Creating buffer with Python

IanMurray — Sat, 11 Dec 2021 21:46:53 GMT

This will probably take a bit of debugging, since I don't have a sample dataset to test on but this should run through each feature dataset in your gdb, copy your feature dataset to you AerialPhotographycoverage.gdb and then run through each feature class in your feature dataset make a buffer and save the buffer in the copied feature dataset in the aerialphotographycoverage.gdb.


# Name: Flight_Line_Buffer.py
# Description: Creates area of Aerial Photography coverage based on digitized flight lines, and associated flight height field in flight line table.

#Import system modules
import arcpy
from arcpy import env

# Set environment settings
env.workspace = "J:\Flight_Lines_GDB\Flight_Lines_Coverage.gdb"
env.Outworkspace = "J:\Aerial_Photo_GDB\Aerial_Photography_Coverage.gdb"

# Create buffer distance output from Flight Height field, and buffer flight lines
PhotoCoverages = "J:\Aerial_Photo_GDB\Aerial_Photography_Coverage.gdb"

fdOutput = "J:\Aerial_Photo_GDB\Aerial_Photography_Coverage.gdb"
#fetches all feaure datasets in workspace into a list
fdlist = arcpy.ListDatasets()

# loop through feature datasets in the list
for fd in fdlist:
    #setting new workspace to the feature dataset we are using
    env.workspace = fd 
 arcpy.CopyManagement(fd , fdOutput + "/" + fd)
    # fetches all feature classes in workspace into a list
    fclist = arcpy.ListFeatureClasses()

    #loop through feature classes in our list
    for fc in fclist:
  FCOutput = fdOutput + "/" + fd
        distanceField = "Flight_Height"
        sideType = "FULL"
        endType = "FLAT"
        dissolveType = "NONE"
        multiplier = 1.502167099846
        cursor = arcpy.SearchCursor(fc)
  count = 1
        for row in cursor:
            distance = ((row.getValue(distanceField))*(multiplier))
            arcpy.Buffer_analysis(fc, FCOutput + "/" + fc + "_Buffer" + str(count) , distance, sideType, endType, dissolveType)
            count += 1

del row 
del cursor

Sorry those buffer parameters get a bit nasty at the end. I needed to set the output path and give each buffer a unique name so it doesn't crash because the same file name exists.

Hope this does the trick for you!

Re: Creating buffer with Python

ToddHowell — Tue, 15 Apr 2014 18:09:44 GMT

So I am getting a error returned for Line 23 which is where the Copy Management tool is called. In messing with the parameters in the tool to see what I could get to work, I had to call a specific feature dataset as the input and then the output could be just the OutWorkspace database. So, I think then the sticking point is creating another for in loop from a dataset list that would process the datasets into the target geodatabase, or is that going to copy over all the feature classes too? I'm sorry for being so bad at this, I'm really new, and took on a pretty ambitious project for my limited abilities. 🙂

Re: Creating buffer with Python

IanMurray — Sat, 11 Dec 2021 21:46:56 GMT

Some of my indents were off, and I changed the environment before copying the feature datasets. I tweaked it a bit, and hopefully it will run. Next time if there is an error, post the error message, it will help with debugging.

# Name: Flight_Line_Buffer.py
# Description: Creates area of Aerial Photography coverage based on digitized flight lines, and associated flight height field in flight line table.

#Import system modules
import arcpy
from arcpy import env

# Set environment settings
env.workspace = "J:\Flight_Lines_GDB\Flight_Lines_Coverage.gdb"
env.Outworkspace = "J:\Aerial_Photo_GDB\Aerial_Photography_Coverage.gdb"

# Create buffer distance output from Flight Height field, and buffer flight lines
PhotoCoverages = "J:\Aerial_Photo_GDB\Aerial_Photography_Coverage.gdb"

fdOutput = "J:\Aerial_Photo_GDB\Aerial_Photography_Coverage.gdb"
#fetches all feaure datasets in workspace into a list
fdlist = arcpy.ListDatasets()

# loop through feature datasets in the list
for fd in fdlist:
    print fd
    #setting new workspace to the feature dataset we are using
    arcpy.CopyManagement(fd , fdOutput + "/" + fd)
    env.workspace = fd 
    # fetches all feature classes in workspace into a list
    fclist = arcpy.ListFeatureClasses()

    #loop through feature classes in our list
    for fc in fclist:
        FCOutput = fdOutput + "/" + fd
        distanceField = "Flight_Height"
        sideType = "FULL"
        endType = "FLAT"
        dissolveType = "NONE"
        multiplier = 1.502167099846
        cursor = arcpy.SearchCursor(fc)
        count = 1
        for row in cursor:
            distance = ((row.getValue(distanceField))*(multiplier))
            arcpy.Buffer_analysis(fc, FCOutput + "/" + fc + "_Buffer" + str(count) , distance, sideType, endType, dissolveType)
            count += 1

    del row 
    del cursor

Re: Creating buffer with Python

ToddHowell — Tue, 15 Apr 2014 20:08:10 GMT

Error:

Runtime error
Traceback (most recent call last):
File "<string>", line 23, in <module>
AttributeError: 'module' object has no attribute 'CopyManagement'

I had noticed those indent errors when I debugged it in PythonWin. The above error is the same one that was returning on the previous script too. I'm not sure if the input and input can be geodatabases in the copy tool. I tried setting up the tool in ArcMap with the parameters specified in the script and it gave an error for the output being a geodatabase, and not wanting to overwrite the OutWorkspace gdb with the input gdb. Should I try to just keep the current workspace .gdb for archival purposes, copy the feature classes out to a working gdb for the sake of simplifying the geoprocessing (removing the element of feature datasets). I think I'm going to write a script for creating a field with the calculated values for the buffer input to simplify that part of the code a bit too. What are your thoughts? Thank you very very much for all your help. I really appreciate you taking your time to teach me so much.

Re: Creating buffer with Python

IanMurray — Tue, 15 Apr 2014 20:49:10 GMT

Now I feel like an idiot.

CopyManagement should have been Copy_management. Replace that and it should work(at least past that point)

Re: Creating buffer with Python

ToddHowell — Wed, 07 May 2014 19:53:28 GMT

Ian,
I have taken a few more ESRI online python trainings, I'm back to trying to debug this script. The current sticking point is as follows:

>>> Eddy_County
Traceback (most recent call last):
File "C:\Python27\ArcGIS10.2\Lib\site-packages\pythonwin\pywin\framework\scriptutils.py", line 326, in RunScript
    exec codeObject in __main__.__dict__
File "C:\Users\thowe01\Desktop\IMURRAY_SCRIPT.py", line 39, in <module>
    distance = ((row.getValue(distanceField))*(multiplier))
File "C:\Program Files (x86)\ArcGIS\Desktop10.2\arcpy\arcpy\arcobjects\arcobjects.py", line 1064, in getValue
    return convertArcObjectToPythonObject(self._arc_object.GetValue(*gp_fixargs(args)))
RuntimeError: ERROR 999999: Error executing function.

I have a few questions/ideas about it as well. I'll wait until you see this before I go muddying the waters with my half cocked ideas though. Hope you are doing well.

Todd

Re: Creating buffer with Python

Zeke — Thu, 08 May 2014 12:21:47 GMT

Can you use row.distanceField instead of row.getValue(distanceField)? Also, make sure distanceField is numeric, not text, although that would probably be a different error.

Re: Creating buffer with Python

ToddHowell — Thu, 08 May 2014 15:26:27 GMT

I'm thinking it might just be easier to start with a script that creates a field for the buffer distance in the feature classes first, also having a field calculator script to use in the future while digitizing the new flight lines. The cursor script for making the calculations seems to be where this is all getting hung up at, right?

Re: Creating buffer with Python

IanMurray — Thu, 08 May 2014 21:09:48 GMT

Got another idea for taking care of that getting that field value. We just have the cursor only iterate through that field so when we set the cursor, set the feature class, then fields you want in brackets, if you needed more then one you can comma seperate each field name(they need to be strings and all inside the brackets). cursor = arcpy.SearchCursor(fc, ["distanceField"]).

In the loop calling an index value on row will not refer back to the original field number i.e. if this was column 5 in your attribute table or index value 4, now it is index value 0(first one in the cursor). If you had another field you were going to iterate through with the cursor listed after this one(say ID field) that would be index value 1, etc. So I put in distance = int(row[0])*(multiplier)) in the for loop instead.

 # Name: Flight_Line_Buffer.py # Description: Creates area of Aerial Photography coverage based on digitized flight lines, and associated flight height field in flight line table.  #Import system modules import arcpy from arcpy import env  # Set environment settings env.workspace = "J:\Flight_Lines_GDB\Flight_Lines_Coverage.gdb" env.Outworkspace = "J:\Aerial_Photo_GDB\Aerial_Photography_Coverage.gdb"  # Create buffer distance output from Flight Height field, and buffer flight lines PhotoCoverages = "J:\Aerial_Photo_GDB\Aerial_Photography_Coverage.gdb"  fdOutput = "J:\Aerial_Photo_GDB\Aerial_Photography_Coverage.gdb" #fetches all feaure datasets in workspace into a list fdlist = arcpy.ListDatasets()  # loop through feature datasets in the list for fd in fdlist:     print fd     #setting new workspace to the feature dataset we are using     arcpy.CopyManagement(fd , fdOutput + "/" + fd)     env.workspace = fd      # fetches all feature classes in workspace into a list     fclist = arcpy.ListFeatureClasses()      #loop through feature classes in our list     for fc in fclist:         FCOutput = fdOutput + "/" + fd         distanceField = "Flight_Height"         sideType = "FULL"         endType = "FLAT"         dissolveType = "NONE"         multiplier = 1.502167099846         cursor = arcpy.SearchCursor(fc, ["distanceField"])         count = 1         for row in cursor:             distance = float(row[0])*(multiplier))             arcpy.Buffer_analysis(fc, FCOutput + "/" + fc + "_Buffer" + str(count) , distance, sideType, endType, dissolveType)             count += 1      del row      del cursor