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containerutils.py
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## This file is part of Invenio.
## Copyright (C) 2012 CERN.
##
## Invenio is free software; you can redistribute it and/or
## modify it under the terms of the GNU General Public License as
## published by the Free Software Foundation; either version 2 of the
## License, or (at your option) any later version.
##
## Invenio is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
## General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with Invenio; if not, write to the Free Software Foundation, Inc.,
## 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
"""
This module contains functions for basic containers (dict, list, str)
"""
def get_substructure(data, path):
"""
Tries to retrieve a sub-structure within some data. If the path does not
match any sub-structure, returns None.
>>> data = {'a': 5, 'b': {'c': [1, 2, [{'f': [57]}], 4], 'd': 'test'}}
>>> get_substructure(island, "bc")
[1, 2, [{'f': [57]}], 4]
>>> get_substructure(island, ['b', 'c'])
[1, 2, [{'f': [57]}], 4]
>>> get_substructure(island, ['b', 'c', 2, 0, 'f', 0])
57
>>> get_substructure(island, ['b', 'c', 2, 0, 'f', 'd'])
None
@param data: a container
@type data: str|dict|list|(an indexable container)
@param path: location of the data
@type path: list|str
@rtype: *
"""
if not len(path):
return data
try:
return get_substructure(data[path[0]], path[1:])
except (TypeError, IndexError, KeyError):
return None
try:
from collections import defaultdict
except:
class defaultdict(dict):
"""
Python 2.4 backport of defaultdict
GPL licensed code taken from NLTK - http://code.google.com/p/nltk/
collections.defaultdict
originally contributed by Yoav Goldberg <yoav.goldberg@gmail.com>
new version by Jason Kirtland from Python cookbook.
<http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/523034>
"""
def __init__(self, default_factory=None, *a, **kw):
if (default_factory is not None and
not hasattr(default_factory, '__call__')):
raise TypeError('first argument must be callable')
dict.__init__(self, *a, **kw)
self.default_factory = default_factory
def __getitem__(self, key):
try:
return dict.__getitem__(self, key)
except KeyError:
return self.__missing__(key)
def __missing__(self, key):
if self.default_factory is None:
raise KeyError(key)
self[key] = value = self.default_factory()
return value
def __reduce__(self):
if self.default_factory is None:
args = tuple()
else:
args = self.default_factory,
return type(self), args, None, None, self.items()
def copy(self):
return self.__copy__()
def __copy__(self):
return type(self)(self.default_factory, self)
def __deepcopy__(self, memo):
import copy
return type(self)(self.default_factory,
copy.deepcopy(self.items()))
def __repr__(self):
return 'defaultdict(%s, %s)' % (self.default_factory,
dict.__repr__(self))

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