node

This package is the successor of zodict.

Overview

Data structures could be described as trees. Some are by nature treeish, like XML documents, LDAP directories or filesystem directory trees, while others can be treated that way.

Furthermore, python has elegant ways for customizing all sorts of datamodel related APIs. 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 order 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. The 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 behaviors. Read the documentation of plumber for details about the plumbing system:

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

>>> @plumbing(
...     Nodespaces,
...     Attributes,
...     Lifecycle,
...     NodeChildValidate,
...     Adopt,
...     DefaultInit,
...     Nodify,
...     OdictStorage)
... class CustomNode(object):
...     pass

>>> dir(CustomNode)
['__class__', '__contains__', '__delattr__', '__delitem__',
'__dict__', '__doc__', '__format__', '__getattribute__',
'__getitem__', '__hash__', '__implemented__', '__init__',
'__iter__', '__len__', '__module__', '__name__',
'__new__', '__nonzero__', '__parent__', '__plumbing__',
'__plumbing_stacks__', '__provides__', '__reduce__',
'__reduce_ex__', '__repr__', '__setattr__', '__setitem__',
'__sizeof__', '__str__', '__subclasshook__', '__weakref__',
'_nodespaces', '_notify_suppress', 'acquire', 'allow_non_node_childs',
'attribute_access_for_attrs', 'attributes', 'attributes_factory',
'attrs', 'clear', 'copy', 'deepcopy', '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 the dir call shows, the CustomNode class was plumbed using given behaviors, so defining a complete INode implementation with some additional behaviours and is now easily done:

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

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

Behaviors

The node package provides several plumbing behaviors:

node.behaviors.DefaultInit

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

node.behaviors.Nodify

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

node.behaviors.Adopt

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

node.behaviors.NodeChildValidate

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

node.behaviors.UnicodeAware

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

node.behaviors.Alias

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

node.behaviors.AsAttrAccess

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

node.behaviors.ChildFactory

Plumbing part providing child factories which are invoked at __getitem__ if object by key is not present at plumbing endpoint yet. See node.interfaces.IChildFactory.

node.behaviors.FixedChildren

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

node.behaviors.GetattrChildren

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

node.behaviors.Nodespaces

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

node.behaviors.Attributes

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

node.behaviors.Lifecycle

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

node.behaviors.AttributesLifecycle

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

node.behaviors.Invalidate

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

node.behaviors.VolatileStorageInvalidate

Plumbing part for invalidating nodes using a volatile storage. See node.interfaces.Invalidate.

node.behaviors.Cache

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

node.behaviors.Order

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

node.behaviors.UUIDAware

Plumbing part providing a uuid on nodes. See node.interfaces.IUUIDAware.

node.behaviors.Reference

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

node.behaviors.Storage

Provide abstract storage access. See node.interfaces.IStorage.

node.behaviors.DictStorage

Provide dictionary storage. See node.interfaces.IStorage.

node.behaviors.OdictStorage

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

Migration

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

It's also useful to take a look at the behaviors the original node is build from.

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

TestCoverage

Summary of the test coverage report:

lines   cov%   module
   51   100%   node.base
   11   100%   node.behaviors.__init__
  107   100%   node.behaviors.alias
   38   100%   node.behaviors.attributes
   65   100%   node.behaviors.cache
  118   100%   node.behaviors.common
   49   100%   node.behaviors.lifecycle
  114   100%   node.behaviors.mapping
   31   100%   node.behaviors.nodespace
   79   100%   node.behaviors.nodify
  108   100%   node.behaviors.order
   80   100%   node.behaviors.reference
   27   100%   node.behaviors.storage
   18   100%   node.events
  124   100%   node.interfaces
   23   100%   node.locking
    1   100%   node.testing.__init__
   62   100%   node.testing.base
   19   100%   node.testing.env
  216   100%   node.testing.fullmapping
   29   100%   node.tests
  130   100%   node.utils

Contributors

• Robert Niederreiter <rnix [at] squarewave [dot] at>
• Florian Friesdorf <flo [at] chaoflow [dot] net>
• Jens Klein <jens [at] bluedynamics [dot] com>