app/soc/logic/dicts.py

   1 #!/usr/bin/python2.5
   2 #
   3 # Copyright 2008 the Melange authors.
   4 #
   5 # Licensed under the Apache License, Version 2.0 (the "License");
   6 # you may not use this file except in compliance with the License.
   7 # You may obtain a copy of the License at
   8 #
   9 #   http://www.apache.org/licenses/LICENSE-2.0
  10 #
  11 # Unless required by applicable law or agreed to in writing, software
  12 # distributed under the License is distributed on an "AS IS" BASIS,
  13 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14 # See the License for the specific language governing permissions and
  15 # limitations under the License.
  16
  17 """Logic related to handling dictionaries
  18 """
  19
  20 __authors__ = [
  21   '"Sverre Rabbelier" <sverre@rabbelier.nl>',
  22   '"Lennard de Rijk" <ljvderijk@gmail.com>',
  23   ]
  24
  25
  26 def filter(target, keys):
  27   """Filters a dictonary to only allow items with the given keys.
  28
  29   Args:
  30     target: The dictionary that is to be filtered
  31     keys: The list with keys to filter the dictionary on
  32
  33   Returns:
  34     A dictionary that only contains the (key,value) from target that have their key in keys
  35   """
  36   result = {}
  37
  38   for key, value in target.iteritems():
  39     if key in keys:
  40       result[key] = value
  41
  42   return result
  43
  44
  45 def merge(target, updates):
  46   """Like the builtin 'update' method but does not overwrite existing values.
  47
  48   Args:
  49     target: The dictionary that is to be updated, may be None
  50     updates: A dictionary containing new values for the original dict
  51
  52   Returns:
  53     the target dict, with any missing values from updates merged in, in-place
  54   """
  55
  56   if not target:
  57     target = {}
  58
  59   for key, value in updates.iteritems():
  60     if key not in target:
  61       target[key] = value
  62
  63   return target
  64
  65
  66 def zip(keys, values):
  67   """Returns a dict containing keys with values.
  68
  69   If there are more items in keys than in values, None will be used.
  70   If there are more items in values than in keys, they will be ignored.
  71
  72   Args:
  73     keys: the keys for the dictionary
  74     values: the values for the dictionary
  75   """
  76
  77   result = {}
  78
  79   size = len(keys)
  80
  81   for i in range(size):
  82     if i < len(values):
  83       value = values[i]
  84     else:
  85       value = None
  86     key = keys[i]
  87     result[key] = value
  88
  89   return result