arcpy_environment_localize.py

"""
  Allows you to pass in a list of environments to get the values of, then pass it back in to reset.
  
  Usage:
  original_envs = store_environments(["workspace","mask"])  # gives back a dict with current environment values for workspace and mask
  arcpy.env.workspace = my_workspace
  arcpy.env.mask = my_raster
  
  # some more code here to do some work with those environments
  
  # When done:
  reset_environments(original_envs)  # sets the environments back to the values stored in the dict retrieved by store_environments
"""

def store_environments(environments_list):
	"""
		Given an iterable of environment variables for arcpy, it stores the current values into a dictionary so they can be reset after an operation
	:param environments_list:
	:return:
	"""
	stored_environments = {}
	for env in environments_list:
		stored_environments[env] = arcpy.env.__getitem__(env)

	return stored_environments


def reset_environments(stored_environments):
	"""
		Given a dict of stored environment variables (from store_environments), it resets the environment values to the value in the dictionary
	:param stored_environments:
	:return:
	"""
	for env in stored_environments.keys():
		arcpy.env.__setitem__(env, stored_environments[env])

I didn't know about the new EnvManager. About time. I've been using the following construct for a while now:

from contextlib import contextmanager

@contextmanager
def env(**kwargs):
    """ context manager for arcpy.env vars """

    old_env = {}
    try:
        for key, val in kwargs.items():
            old_env[key] = getattr(arcpy.env, key)
            setattr(arcpy.env, key, val)

        yield

    except Exception:
        raise

    finally:
        for key, val in old_env.items():
            setattr(arcpy.env, key, val)