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"""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)
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