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"""A collection of modules for iterating through different kinds of
tree, generating tokens identical to those produced by the tokenizer
To create a tree walker for a new type of tree, you need to do
implement a tree walker object (called TreeWalker by convention) that
implements a 'serialize' method taking a tree as sole argument and
returning an iterator generating tokens.
treeWalkerCache = {}
def getTreeWalker(treeType, implementation=None, **kwargs):
"""Get a TreeWalker 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", "etree" and "beautifulsoup"
"simpletree" - a built-in DOM-ish tree type with support for some
more pythonic idioms.
"dom" - The xml.dom.minidom DOM implementation
"pulldom" - The xml.dom.pulldom event stream
"etree" - A generic walker for tree implementations exposing an
elementtree-like interface (known to work with
ElementTree, cElementTree and lxml.etree).
"lxml" - Optimized walker for lxml.etree
"beautifulsoup" - Beautiful soup (if installed)
"genshi" - a Genshi stream
implementation - (Currently applies to the "etree" tree type only). A module
implementing the tree type e.g. xml.etree.ElementTree or
treeType = treeType.lower()
if treeType not in treeWalkerCache:
if treeType in ("dom", "pulldom", "simpletree"):
mod = __import__(treeType, globals())
treeWalkerCache[treeType] = mod.TreeWalker
elif treeType == "genshi":
import genshistream
treeWalkerCache[treeType] = genshistream.TreeWalker
elif treeType == "beautifulsoup":
import soup
treeWalkerCache[treeType] = soup.TreeWalker
elif treeType == "lxml":
import lxmletree
treeWalkerCache[treeType] = lxmletree.TreeWalker
elif treeType == "etree":
import etree
# XXX: NEVER cache here, caching is done in the etree submodule
return etree.getETreeModule(implementation, **kwargs).TreeWalker
return treeWalkerCache.get(treeType)