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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.simpletree.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
The supplied simpletree module provides a python-only implementation
of a full treebuilder and is a useful reference for the semantics of
the various methods.
"""
from __future__ import absolute_import, division, unicode_literals
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 "simpletree", "dom", and "etree"
"simpletree" - a built-in DOM-ish tree type with support for some
more pythonic idioms.
"dom" - A generic builder for DOM implementations, defaulting to
a xml.dom.minidom based implementation for the sake of
backwards compatibility (as releases up until 0.10 had a
builder called "dom" that was a minidom implemenation).
"etree" - A generic builder for tree implementations exposing an
elementtree-like interface (known to work with
ElementTree, cElementTree and lxml.etree).
implementation - (Currently applies to the "etree" and "dom" tree types). A
module implementing the tree type e.g.
xml.etree.ElementTree or lxml.etree."""
treeType = treeType.lower()
if treeType not in treeBuilderCache:
if treeType == "dom":
from . import dom
# XXX: Keep backwards compatibility by using minidom if no implementation is given
if implementation is None:
from xml.dom import minidom
implementation = minidom
# XXX: NEVER cache here, caching is done in the dom submodule
return dom.getDomModule(implementation, **kwargs).TreeBuilder
elif treeType == "simpletree":
from . import simpletree
treeBuilderCache[treeType] = simpletree.TreeBuilder
elif treeType == "lxml":
from . import etree_lxml
treeBuilderCache[treeType] = etree_lxml.TreeBuilder
elif treeType == "etree":
# Come up with a sane default
if implementation is None:
try:
import xml.etree.cElementTree as ET
except ImportError:
try:
import xml.etree.ElementTree as ET
except ImportError:
try:
import cElementTree as ET
except ImportError:
import elementtree.ElementTree as ET
implementation = ET
from . import 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)