"""A collection of modules for iterating through different kinds of
tree, generating tokens identical to those produced by the tokenizer
module.
To create a tree walker for a new type of tree, you need to
implement a tree walker object (called TreeWalker by convention) that
implements a 'serialize' method which takes a tree as sole argument and
returns an iterator which generates tokens.
"""
from __future__ import absolute_import, division, unicode_literals
from .. import constants
from .._utils import default_etree
__all__ = ["getTreeWalker", "pprint"]
treeWalkerCache = {}
[docs]def getTreeWalker(treeType, implementation=None, **kwargs):
"""Get a TreeWalker class for various types of tree with built-in support
:arg str treeType: the name of the tree type required (case-insensitive).
Supported values are:
* "dom": The xml.dom.minidom DOM implementation
* "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
* "genshi": a Genshi stream
:arg implementation: A module implementing the tree type e.g.
xml.etree.ElementTree or cElementTree (Currently applies to the "etree"
tree type only).
:arg kwargs: keyword arguments passed to the etree walker--for other
walkers, this has no effect
:returns: a TreeWalker class
"""
treeType = treeType.lower()
if treeType not in treeWalkerCache:
if treeType == "dom":
from . import dom
treeWalkerCache[treeType] = dom.TreeWalker
elif treeType == "genshi":
from . import genshi
treeWalkerCache[treeType] = genshi.TreeWalker
elif treeType == "lxml":
from . import etree_lxml
treeWalkerCache[treeType] = etree_lxml.TreeWalker
elif treeType == "etree":
from . import etree
if implementation is None:
implementation = default_etree
# XXX: NEVER cache here, caching is done in the etree submodule
return etree.getETreeModule(implementation, **kwargs).TreeWalker
return treeWalkerCache.get(treeType)
def concatenateCharacterTokens(tokens):
pendingCharacters = []
for token in tokens:
type = token["type"]
if type in ("Characters", "SpaceCharacters"):
pendingCharacters.append(token["data"])
else:
if pendingCharacters:
yield {"type": "Characters", "data": "".join(pendingCharacters)}
pendingCharacters = []
yield token
if pendingCharacters:
yield {"type": "Characters", "data": "".join(pendingCharacters)}
[docs]def pprint(walker):
"""Pretty printer for tree walkers
Takes a TreeWalker instance and pretty prints the output of walking the tree.
:arg walker: a TreeWalker instance
"""
output = []
indent = 0
for token in concatenateCharacterTokens(walker):
type = token["type"]
if type in ("StartTag", "EmptyTag"):
# tag name
if token["namespace"] and token["namespace"] != constants.namespaces["html"]:
if token["namespace"] in constants.prefixes:
ns = constants.prefixes[token["namespace"]]
else:
ns = token["namespace"]
name = "%s %s" % (ns, token["name"])
else:
name = token["name"]
output.append("%s<%s>" % (" " * indent, name))
indent += 2
# attributes (sorted for consistent ordering)
attrs = token["data"]
for (namespace, localname), value in sorted(attrs.items()):
if namespace:
if namespace in constants.prefixes:
ns = constants.prefixes[namespace]
else:
ns = namespace
name = "%s %s" % (ns, localname)
else:
name = localname
output.append("%s%s=\"%s\"" % (" " * indent, name, value))
# self-closing
if type == "EmptyTag":
indent -= 2
elif type == "EndTag":
indent -= 2
elif type == "Comment":
output.append("%s<!-- %s -->" % (" " * indent, token["data"]))
elif type == "Doctype":
if token["name"]:
if token["publicId"]:
output.append("""%s<!DOCTYPE %s "%s" "%s">""" %
(" " * indent,
token["name"],
token["publicId"],
token["systemId"] if token["systemId"] else ""))
elif token["systemId"]:
output.append("""%s<!DOCTYPE %s "" "%s">""" %
(" " * indent,
token["name"],
token["systemId"]))
else:
output.append("%s<!DOCTYPE %s>" % (" " * indent,
token["name"]))
else:
output.append("%s<!DOCTYPE >" % (" " * indent,))
elif type == "Characters":
output.append("%s\"%s\"" % (" " * indent, token["data"]))
elif type == "SpaceCharacters":
assert False, "concatenateCharacterTokens should have got rid of all Space tokens"
else:
raise ValueError("Unknown token type, %s" % type)
return "\n".join(output)