Projects feature classes to Web Mercator (Auxiliary Sphere) if they are not in it already.

projectFtrsForWeb.py

#
# @date 24/03/2015
# @author Cindy Williams
#
# Projects feature classes to Web Mercator (Auxiliary Sphere)
# if they are not in it already.
#
# For use as a standalone script.
#

import arcpy
import os

arcpy.env.workspace = r"C:\Database Connections\work.sde"
# Create spatial reference using the WKID
sr_web = arcpy.SpatialReference(3857)
gdb = r"C:\Some\Arb\Folder\web.gdb"
fds_list = [] # List for existing feature datasets

# Loop over all feature datasets in workspace
for fds in arcpy.ListDatasets(feature_type="Feature"):
    desc = arcpy.Describe(fds)
    # Check if the spatial reference of the feature dataset
    # is different to 3857
    if desc.spatialReference.name != sr_web.name:
        fds_list.append(fds)

# Loop over feature datasets in list
for fd in fds_list:
    # Create a copy of it with correct projection
	arcpy.management.CreateFeatureDataset(gdb,
					      fd.rpartition(".")[2],
					      sr_web)
	print("Created feature dataset: " + fd)
	# Loop over feature classes within the feature dataset
	# within the workspace
	for ftr in arcpy.ListFeatureClasses(feature_dataset=fd):
	    # Project the feature classes to the respective
	    # feature dataset in the new gdb
		arcpy.management.Project(ftr,
					 os.path.join(gdb, fd.rpartition(".")[2], ftr.rpartition(".")[2]),
					 sr_web)
		print("\tProjected " + ftr)
print("Script complete.")