146 lines
5.1 KiB
ReStructuredText
146 lines
5.1 KiB
ReStructuredText
:mod:`xml.dom.pulldom` --- Support for building partial DOM trees
|
|
=================================================================
|
|
|
|
.. module:: xml.dom.pulldom
|
|
:synopsis: Support for building partial DOM trees from SAX events.
|
|
|
|
.. moduleauthor:: Paul Prescod <paul@prescod.net>
|
|
|
|
**Source code:** :source:`Lib/xml/dom/pulldom.py`
|
|
|
|
--------------
|
|
|
|
The :mod:`xml.dom.pulldom` module provides a "pull parser" which can also be
|
|
asked to produce DOM-accessible fragments of the document where necessary. The
|
|
basic concept involves pulling "events" from a stream of incoming XML and
|
|
processing them. In contrast to SAX which also employs an event-driven
|
|
processing model together with callbacks, the user of a pull parser is
|
|
responsible for explicitly pulling events from the stream, looping over those
|
|
events until either processing is finished or an error condition occurs.
|
|
|
|
|
|
.. warning::
|
|
|
|
The :mod:`xml.dom.pulldom` module is not secure against
|
|
maliciously constructed data. If you need to parse untrusted or
|
|
unauthenticated data see :ref:`xml-vulnerabilities`.
|
|
|
|
.. versionchanged:: 3.7.1
|
|
|
|
The SAX parser no longer processes general external entities by default to
|
|
increase security by default. To enable processing of external entities,
|
|
pass a custom parser instance in::
|
|
|
|
from xml.dom.pulldom import parse
|
|
from xml.sax import make_parser
|
|
from xml.sax.handler import feature_external_ges
|
|
|
|
parser = make_parser()
|
|
parser.setFeature(feature_external_ges, True)
|
|
parse(filename, parser=parser)
|
|
|
|
|
|
Example::
|
|
|
|
from xml.dom import pulldom
|
|
|
|
doc = pulldom.parse('sales_items.xml')
|
|
for event, node in doc:
|
|
if event == pulldom.START_ELEMENT and node.tagName == 'item':
|
|
if int(node.getAttribute('price')) > 50:
|
|
doc.expandNode(node)
|
|
print(node.toxml())
|
|
|
|
``event`` is a constant and can be one of:
|
|
|
|
* :data:`START_ELEMENT`
|
|
* :data:`END_ELEMENT`
|
|
* :data:`COMMENT`
|
|
* :data:`START_DOCUMENT`
|
|
* :data:`END_DOCUMENT`
|
|
* :data:`CHARACTERS`
|
|
* :data:`PROCESSING_INSTRUCTION`
|
|
* :data:`IGNORABLE_WHITESPACE`
|
|
|
|
``node`` is an object of type :class:`xml.dom.minidom.Document`,
|
|
:class:`xml.dom.minidom.Element` or :class:`xml.dom.minidom.Text`.
|
|
|
|
Since the document is treated as a "flat" stream of events, the document "tree"
|
|
is implicitly traversed and the desired elements are found regardless of their
|
|
depth in the tree. In other words, one does not need to consider hierarchical
|
|
issues such as recursive searching of the document nodes, although if the
|
|
context of elements were important, one would either need to maintain some
|
|
context-related state (i.e. remembering where one is in the document at any
|
|
given point) or to make use of the :func:`DOMEventStream.expandNode` method
|
|
and switch to DOM-related processing.
|
|
|
|
|
|
.. class:: PullDom(documentFactory=None)
|
|
|
|
Subclass of :class:`xml.sax.handler.ContentHandler`.
|
|
|
|
|
|
.. class:: SAX2DOM(documentFactory=None)
|
|
|
|
Subclass of :class:`xml.sax.handler.ContentHandler`.
|
|
|
|
|
|
.. function:: parse(stream_or_string, parser=None, bufsize=None)
|
|
|
|
Return a :class:`DOMEventStream` from the given input. *stream_or_string* may be
|
|
either a file name, or a file-like object. *parser*, if given, must be an
|
|
:class:`~xml.sax.xmlreader.XMLReader` object. This function will change the
|
|
document handler of the
|
|
parser and activate namespace support; other parser configuration (like
|
|
setting an entity resolver) must have been done in advance.
|
|
|
|
If you have XML in a string, you can use the :func:`parseString` function instead:
|
|
|
|
.. function:: parseString(string, parser=None)
|
|
|
|
Return a :class:`DOMEventStream` that represents the (Unicode) *string*.
|
|
|
|
.. data:: default_bufsize
|
|
|
|
Default value for the *bufsize* parameter to :func:`parse`.
|
|
|
|
The value of this variable can be changed before calling :func:`parse` and
|
|
the new value will take effect.
|
|
|
|
.. _domeventstream-objects:
|
|
|
|
DOMEventStream Objects
|
|
----------------------
|
|
|
|
.. class:: DOMEventStream(stream, parser, bufsize)
|
|
|
|
|
|
.. method:: getEvent()
|
|
|
|
Return a tuple containing *event* and the current *node* as
|
|
:class:`xml.dom.minidom.Document` if event equals :data:`START_DOCUMENT`,
|
|
:class:`xml.dom.minidom.Element` if event equals :data:`START_ELEMENT` or
|
|
:data:`END_ELEMENT` or :class:`xml.dom.minidom.Text` if event equals
|
|
:data:`CHARACTERS`.
|
|
The current node does not contain information about its children, unless
|
|
:func:`expandNode` is called.
|
|
|
|
.. method:: expandNode(node)
|
|
|
|
Expands all children of *node* into *node*. Example::
|
|
|
|
from xml.dom import pulldom
|
|
|
|
xml = '<html><title>Foo</title> <p>Some text <div>and more</div></p> </html>'
|
|
doc = pulldom.parseString(xml)
|
|
for event, node in doc:
|
|
if event == pulldom.START_ELEMENT and node.tagName == 'p':
|
|
# Following statement only prints '<p/>'
|
|
print(node.toxml())
|
|
doc.expandNode(node)
|
|
# Following statement prints node with all its children '<p>Some text <div>and more</div></p>'
|
|
print(node.toxml())
|
|
|
|
.. method:: DOMEventStream.reset()
|
|
|