node 0.9.3

The node

node

This package is the successor of zodict.

Overview

Data structures could be described as tree. Some are by nature treeish, like XML documents, LDAP directories or filesystem directory trees, while others could be treaten as. Consider SQL as example. A Database has tables, these contain rows which contain columns.

Next, python has elegant ways for customizing all sorts of datamodel related API. The dictionary container type fits almost completely the purpose of representing a node of a tree. The same API is also described in zope.interface.common.mapping.IFullMapping. Additionaly a node must provide hierarchy information. In this case the contract of zope.location.interfaces.ILocation is used.

Having data structures as such trees has some advantages:

• Unified data access API to different data models and/or sources

• Trees are traversable in both directions

• Once in memory, node trees are fast to deal with

• Software working on node trees may not need to know about internal data structures, as long as the node tree implementation provides the correct interface contracts

Usage

node ships with some “ready-to-import-and-use” nodes.

An unordered node. This can be used as base for trees where oder of items doesn’t matter.:

>>> from node.base import BaseNode
>>> root = BaseNode(name='root')
>>> root['child'] = BaseNode()
>>> root.printtree()
<class 'node.base.BaseNode'>: root
  <class 'node.base.BaseNode'>: child

An ordered node. Order of items is preserved.:

>>> from node.base import OrderedNode
>>> root = OrderedNode(name='orderedroot')
>>> root['foo'] = OrderedNode()
>>> root['bar'] = OrderedNode()
>>> root.printtree()
<class 'node.base.OrderedNode'>: orderedroot
  <class 'node.base.OrderedNode'>: foo
  <class 'node.base.OrderedNode'>: bar

>>> root.items()
[('foo', <OrderedNode object 'foo' at ...>),
('bar', <OrderedNode object 'bar' at ...>)]

A full API description of the node interface can be found at node.interfaces.INode.

A more fine granular control of node functionality

node utilizes the plumber package.

Thus, different behaviors of nodes are provided by plumbing parts. Read the documentation of plumber for details about the plumbing system.

>>> from plumber import plumber
>>> from node.parts import (
...     Nodespaces,
...     Attributes,
...     Lifecycle,
...     NodeChildValidate,
...     Adopt,
...     DefaultInit,
...     Nodify,
...     OdictStorage,
... )

>>> class CustomNode(object):
...     __metaclass__ = plumber
...     __plumbing__ = (
...         Nodespaces,
...         Attributes,
...         Lifecycle,
...         NodeChildValidate,
...         Adopt,
...         DefaultInit,
...         Nodify,
...         OdictStorage,
...     )

>>> dir(CustomNode)
['__class__', '__contains__', '__delattr__', '__delitem__',
'__dict__', '__doc__', '__format__', '__getattribute__',
'__getitem__', '__hash__', '__implemented__', '__init__',
'__iter__', '__len__', '__metaclass__', '__module__', '__name__',
'__new__', '__nonzero__', '__parent__', '__plumbing__',
'__plumbing_stacks__', '__provides__', '__reduce__',
'__reduce_ex__', '__repr__', '__setattr__', '__setitem__',
'__sizeof__', '__str__', '__subclasshook__', '__weakref__',
'_nodespaces', '_notify_suppress', 'allow_non_node_childs',
'attribute_access_for_attrs', 'attributes', 'attributes_factory',
'attrs', 'clear', 'copy', 'detach', 'events', 'filtereditems',
'filtereditervalues', 'filteredvalues', 'get', 'has_key', 'items',
'iteritems', 'iterkeys', 'itervalues', 'keys', 'name', 'noderepr',
'nodespaces', 'parent', 'path', 'pop', 'popitem', 'printtree',
'root', 'setdefault', 'storage', 'update', 'values']

As dir call shows, CustomNode class was plumbed using given parts, now defining a complete INode implementation with some additional behaviours and is now ready to use:

>>> node = CustomNode()
>>> node['child'] = CustomNode()
>>> node.printtree()
<class 'CustomNode'>: None
  <class 'CustomNode'>: child

>>> from node.interfaces import INode
>>> INode.providedBy(node)
True

Parts

node package provides several plumbing parts:

node.parts.DefaultInit

Plumbing part providing default __init__ function on node. See node.interfaces.IDefaultInit.

node.parts.Nodify

Plumbing part to Fill in gaps for full INode API. See node.interfaces.INodify.

node.parts.Adopt

Plumbing part that provides adoption of children. See node.interfaces.IAdopt.

node.parts.NodeChildValidate

Plumbing part for child node validation. See node.interfaces.INodeChildValidate.

node.parts.UnicodeAware

Plumbing part to ensure unicode for keys and string values. See node.interfaces.IUnicodeAware.

node.parts.Alias

Plumbing part that provides aliasing of child keys. See node.interfaces.IAlias.

node.parts.AsAttrAccess

Plumbing part to get node as IAttributeAccess implementation. See node.interfaces.IAsAttrAccess.

node.parts.FixedChildren

Plumbing part that initializes a fixed dictionary as children. See node.interfaces.IFixedChildren.

node.parts.GetattrChildren

Plumbing part for child access via __getattr__, given the attribute name is unused. See node.interfaces.IGetattrChildren.

node.parts.Nodespaces

Plumbing part for providing nodespaces on node. See node.interfaces.INodespaces.

node.parts.Attributes

Plumbing part to provide attributes on node. Requires node.parts.Nodespaces part. See node.interfaces.IAttributes.

node.parts.Lifecycle

Plumbing part taking care of lifecycle events. See node.interfaces.ILifecycle.

node.parts.AttributesLifecycle

Plumbing part for handling ifecycle events at attributes manipulation. See node.interfaces.IAttributesLifecycle.

node.parts.Invalidate

Plumbing part for node invalidation. See node.interfaces.Invalidate.

node.parts.Cache

Plumbing part for caching. See node.interfaces.ICache.

node.parts.Order

Plumbing part for ordering support. See node.interfaces.IOrder.

node.parts.Reference

Plumbing part holding an index of all nodes contained in the tree. See node.interfaces.IReference.

node.parts.DictStorage

Provide dictionary storage. See node.interfaces.IStorage.

node.parts.OdictStorage

Provide ordered dictionary storage. See node.interfaces.IStorage.

Migration

A node which behaves like zodict.Node is contained at node.base.Node. This node is supposed to be used for migration from zodict.

It’s also useful to take a look of which parts the original node is build of.

Probably an implementation does not need all the parts at once. In this case define the node plumbing directly on node class instead of inheriting from node.base.Node.

TestCoverage

Summary of the test coverage report:

lines   cov%   module
  106    72%   node.aliasing
   53   100%   node.base
   14   100%   node.events
  125   100%   node.interfaces
   23   100%   node.locking
   11   100%   node.parts.__init__
   46   100%   node.parts.alias
   38   100%   node.parts.attributes
   50   100%   node.parts.cache
   83   100%   node.parts.common
   52   100%   node.parts.lifecycle
  113   100%   node.parts.mapping
   31   100%   node.parts.nodespace
   70   100%   node.parts.nodify
   65   100%   node.parts.order
   81   100%   node.parts.reference
   27   100%   node.parts.storage
    1   100%   node.testing.__init__
   62   100%   node.testing.base
  214   100%   node.testing.fullmapping
    1   100%   node.tests.__init__
   19   100%   node.tests.env
   31   100%   node.tests.test_node
  109   100%   node.utils

Contributors

• Robert Niederreiter <[e-mail]>

• Florian Friesdorf <[e-mail]>

• Jens Klein <[e-mail]>

Changes

0.9.3

• Increase test coverage [rnix, 2011-05-09]

• Add interfaces IFixedChildren and IGetattrChildren for related parts. [rnix, 2011-05-09]

• Rename Unicode part to UnicodeAware. [rnix, 2011-05-09]

• Add node.utils.StrCodec. [rnix, 2011-05-09]

• Inherit INodify interface from INode. [rnix, 2011-05-08]

• Locking tests. Add time.sleep after thread start. [rnix, 2011-05-08]

• Cleanup BaseTester, remove sorted_output flag (always sort), also search class bases for detection in wherefrom. [rnix, 2011-05-08]

• Remove useless try/except in utils.AttributeAccess. [rnix, 2011-05-08]

• Add instance_property decorator to utils. [rnix, 2011-05-06]

• Add FixedChildren and GetattrChildren parts. [chaoflow, 2011-04-22]

0.9.2

• Add __nonzero__ on Nodifiy part always return True. [rnix, 2011-03-15]

0.9.1

• Provide node.base.Node with same behavior like zodict.Node for migration purposes. [rnix, 2011-02-08]

0.9

• Make it work [rnix, chaoflow, et al]

License

Copyright (c) 2010, BlueDynamics Alliance, Austria All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

• Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

• Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

• Neither the name of the BlueDynamics Alliance nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY BlueDynamics Alliance AS IS AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL BlueDynamics Alliance BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.