"""A collection of modules for building different kinds of tree from HTML documents. To create a treebuilder for a new type of tree, you need to do implement several things: 1) A set of classes for various types of elements: Document, Doctype, Comment, Element. These must implement the interface of _base.treebuilders.Node (although comment nodes have a different signature for their constructor, see treebuilders.etree.Comment) Textual content may also be implemented as another node type, or not, as your tree implementation requires. 2) A treebuilder object (called TreeBuilder by convention) that inherits from treebuilders._base.TreeBuilder. This has 4 required attributes: documentClass - the class to use for the bottommost node of a document elementClass - the class to use for HTML Elements commentClass - the class to use for comments doctypeClass - the class to use for doctypes It also has one required method: getDocument - Returns the root node of the complete document tree 3) If you wish to run the unit tests, you must also create a testSerializer method on your treebuilder which accepts a node and returns a string containing Node and its children serialized according to the format used in the unittests """ from __future__ import absolute_import, division, unicode_literals from ..utils import default_etree treeBuilderCache = {} def getTreeBuilder(treeType, implementation=None, **kwargs): """Get a TreeBuilder class for various types of tree with built-in support treeType - the name of the tree type required (case-insensitive). Supported values are: "dom" - A generic builder for DOM implementations, defaulting to a xml.dom.minidom based implementation. "etree" - A generic builder for tree implementations exposing an ElementTree-like interface, defaulting to xml.etree.cElementTree if available and xml.etree.ElementTree if not. "lxml" - A etree-based builder for lxml.etree, handling limitations of lxml's implementation. implementation - (Currently applies to the "etree" and "dom" tree types). A module implementing the tree type e.g. xml.etree.ElementTree or xml.etree.cElementTree.""" treeType = treeType.lower() if treeType not in treeBuilderCache: if treeType == "dom": from . import dom # Come up with a sane default (pref. from the stdlib) if implementation is None: from xml.dom import minidom implementation = minidom # NEVER cache here, caching is done in the dom submodule return dom.getDomModule(implementation, **kwargs).TreeBuilder elif treeType == "lxml": from . import etree_lxml treeBuilderCache[treeType] = etree_lxml.TreeBuilder elif treeType == "etree": from . import etree if implementation is None: implementation = default_etree # NEVER cache here, caching is done in the etree submodule return etree.getETreeModule(implementation, **kwargs).TreeBuilder else: raise ValueError("""Unrecognised treebuilder "%s" """ % treeType) return treeBuilderCache.get(treeType)