:mod:!xml.dom.pulldom --- Support for building partial DOM trees

.. module:: xml.dom.pulldom :synopsis: Support for building partial DOM trees from SAX events.

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.

.. note::

If you need to parse untrusted or unauthenticated data, see :ref:xml-security.

.. 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)

.. versionchanged:: 3.11 Support for :meth:~object.__getitem__ method has been removed.

.. 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()