Example: Check for Existences
from arcpy import env
env.workspace = r"c:\temp"
fc = sample.shp
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.