Tuesday, May 17, 2011

Checking the Existence of Data

To check if data exists using the arcpy module, use the Exists().  This function tests for the existence of feature classes, tables, data sets, shapefiles, workspaces, layers, and other files in the current workspace at the time of execution.  The function will return a Boolean value (true/false) to let the end user know if the file exists.

Example: Check for Existences

import arcpy
from arcpy import env

env.workspace = r"c:\temp"
fc = sample.shp
if arcpy.Exists(fc):
   print "The sample.shp does exist"
   print "The sample.shp does not exist"

By default, when scripting, the results of any script or existing data is not to overwrite the data. To change that behavior, set the env.overwriteOutput to True. If data exists and the overwrite property is not set, it could cause an error to the thrown.