#!/usr/bin/python2.5

#

# Copyright 2008 the Melange authors.

#

# Licensed under the Apache License, Version 2.0 (the "License");

# you may not use this file except in compliance with the License.

# You may obtain a copy of the License at

#

#   http://www.apache.org/licenses/LICENSE-2.0

#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS,

# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

# See the License for the specific language governing permissions and

# limitations under the License.

"""Logic related to handling dictionaries

"""

__authors__ = [

  '"Sverre Rabbelier" <sverre@rabbelier.nl>',

  ]

def merge(target, updates):

  """Like the builtin 'update' method but does not overwrite existing values

  Args:

    target: The dictionary that is to be updated, may be None

    updates: A dictionary containing new values for the original dict

  Returns:

    the target dict, with any missing values from updates merged in, in-place 

  """

  if not target:

    target = {}

  for key, value in updates.iteritems():

    if key not in target:

      target[key] = value

  return target