topic Re: Loop for exporting shapefiles from an existing shapefile in Python Questions

Loop for exporting shapefiles from an existing shapefile

KONPETROV — Wed, 18 Mar 2015 15:26:42 GMT

Hello i have a pnt shp with 50 pnts. I want to export each one of it in a separate shapefile with arcpy writting a loop. My problem is that i want the output name i create to have a different name, e.g. for 1st pnt i want the output layers' name to be pnt1_lyr, for the 2nd point, pnt2_lyr etc. I wrote that code but i always have an error. Can someone correct me;

import arcpy

arcpy.env.workspace = "c:/Wing/Sk"

for i in range(0, 49):

arcpy.MakeFeatureLayer_management("spatially50.shp", "pnt_" + i + "lyr", "FID = i")

Thank you very much

Re: Loop for exporting shapefiles from an existing shapefile

IanMurray — Wed, 18 Mar 2015 15:37:11 GMT

If you are needing to make a new shapefile, then you are using the wrong geoprocessing tool. Make Feature Layer creates a layer in memory for use in a map document, not a new shapefile. Try using Feature Class to Feature Class tool, this can create new shapefiles on your hard drive.

Also if you are having an error in your code, please post the error so it helps us understand what is going wrong.

Re: Loop for exporting shapefiles from an existing shapefile

JoshuaBixby — Wed, 18 Mar 2015 15:39:24 GMT

First, I don't think MakeFeatureLayer_management is what you want unless you are using it as an intermediate step before exporting the feature layer.

Second, it helps to paste specific error messages.

Third, what about putting str(i) in place of i in the layer name you are concatenating.

Re: Loop for exporting shapefiles from an existing shapefile

KONPETROV — Wed, 18 Mar 2015 16:10:27 GMT

oh, i thought that i would create a shepfile form an attribute od an another shapefile i should use make new feature layer. Although i knew i would have it only in memore and not in hard drive. Ok i propably must do that as you decribe thank you.

Re: Loop for exporting shapefiles from an existing shapefile

DarrenWiens2 — Wed, 18 Mar 2015 16:10:56 GMT

Just to pile on, your where clause "FID = i" literally translates to "where FID = the letter i" (well, technically the number i because it's not within quotes). There are A LOT of discussions on here about how to make a where clause incorporating a variable, and where to put the quotation marks to make it function properly, but I believe it should be as simple as: "FID = " + str(i).

Re: Loop for exporting shapefiles from an existing shapefile

KONPETROV — Wed, 18 Mar 2015 16:12:06 GMT

For the Make Feature Layer you are right, thank you both. I tried it with str(i) and i have again the same message that i cannot use it for FID = i!

This is it:

Runtime error Traceback (most recent call last): File "<string>", line 4, in <module> File "c:\program files (x86)\arcgis\desktop10.2\arcpy\arcpy\management.py", line 6043, in MakeFeatureLayer raise e ExecuteError: ERROR 000230: Failed selecting with FID = i Failed to execute (MakeFeatureLayer)

Re: Loop for exporting shapefiles from an existing shapefile

KONPETROV — Wed, 18 Mar 2015 16:13:27 GMT

Oh ,so it's not totally wrong?

Re: Loop for exporting shapefiles from an existing shapefile

DarrenWiens2 — Wed, 18 Mar 2015 16:15:00 GMT

Well, it is wrong in the sense that you're not using as a variable (values 0-50), you're using it always as the value 'i'.

Re: Loop for exporting shapefiles from an existing shapefile

KONPETROV — Wed, 18 Mar 2015 16:32:23 GMT

Ok i tried that with feature class to feature class you are right this is what i e=wanted. But i still have the same problem. How can i create a loop for 50 pnts for that? I am posting you my new code

import arcpy

from arcpy import env

env.workspace = "c:/Wing/Sk"

arcpy.FeatureClassToFeatureClass_conversion("spatially50", "c:/Wing/Sk", "pnt1", "FID=0")

Re: Loop for exporting shapefiles from an existing shapefile

DarrenWiens2 — Sat, 11 Dec 2021 23:54:08 GMT

Untested, but should be something like:

import arcpy
from arcpy import env
env.workspace = "c:/Wing/Sk"
for i in range(50):
    arcpy.FeatureClassToFeatureClass_conversion("spatially50", "c:/Wing/Sk", "pnt" + str(i), "FID=" + str(i))

Re: Loop for exporting shapefiles from an existing shapefile

IanMurray — Sat, 11 Dec 2021 23:54:10 GMT

actually FID is a numeric field, so a str(i) there would crash the query clause, since its comparing a number to a string.

I made some sample data and tested the following that works.

import arcpy
arcpy.env.workspace = "c:/Wing/Sk"
for i in range(0, 50):
  where_clause = "FID = {}".format(i)
  arcpy.FeatureClassToFeatureClass_conversion("spatially50", "c:/Wing/Sk", "pnt" + str(i), where_clause)

Formatting queries in python can be annoying, string formatting makes this much easier.

I usually refer back to this thread for properly creating SQL queries Python - Select by attributes query issue

Re: Loop for exporting shapefiles from an existing shapefile

DarrenWiens2 — Wed, 18 Mar 2015 17:07:42 GMT

actually FID is a numeric field, so a str(i) there would crash the query clause, since its comparing a number to a string.

No. " FID = " + str(i) results in a whereclause of " FID = 0 " (desired) not " FID = '0' " (what you predict). Your method may work, but so does mine.

Re: Loop for exporting shapefiles from an existing shapefile

IanMurray — Wed, 18 Mar 2015 17:15:26 GMT

Sorry you were completely right about that, and to boot its faster since you aren't setting a variable each time.

Re: Loop for exporting shapefiles from an existing shapefile

JoshuaBixby — Sat, 11 Dec 2021 23:54:13 GMT

If you are only working with Points, another approach is to use the new NumPy-based features that were introduced with the ArcPy data access (arcpy.da) module.

import os
import numpy as np

in_features = #Point data set to have exported as individual data sets
out_path = #Path to geodatabases or folder for individual data sets
out_prefix = 'pnt_'  #Prefix for individual data sets, can be empty ''

desc = arcpy.Describe(in_features)
SR = desc.spatialReference
OID_name = desc.OIDFieldName
shape_name = desc.ShapeFieldName

narr = arcpy.da.FeatureClassToNumPyArray(in_features, "*")
ndtype = narr.dtype
for row in narr:
    n = np.array(row, ndtype)
    OID = n[OID_name]
    arcpy.da.NumPyArrayToFeatureClass(n,
                                      os.path.join(out_path, out_prefix + str(OID)),
                                      shape_name,
                                      SR)

The above script will work on shape files and feature classes because I am using an arcpy.Describe object to retrieve the name of the unique identifier and shape fields.

Re: Loop for exporting shapefiles from an existing shapefile

KONPETROV — Wed, 18 Mar 2015 20:03:45 GMT

i was missing that: "FID=" + str(i). For God that was really helpfull, thank you for your try Mr. Wiens.

Re: Loop for exporting shapefiles from an existing shapefile

KONPETROV — Wed, 18 Mar 2015 20:10:59 GMT

Thank you a lot Mr. Bixby