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Diffstat (limited to 'Doc/library/xml.dom.pulldom.rst')
| -rw-r--r-- | Doc/library/xml.dom.pulldom.rst | 87 |
1 files changed, 69 insertions, 18 deletions
diff --git a/Doc/library/xml.dom.pulldom.rst b/Doc/library/xml.dom.pulldom.rst index 4a5ef4c135..eb16a0933d 100644 --- a/Doc/library/xml.dom.pulldom.rst +++ b/Doc/library/xml.dom.pulldom.rst @@ -9,34 +9,72 @@ -------------- -:mod:`xml.dom.pulldom` allows building only selected portions of a Document -Object Model representation of a document from SAX events. +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. +Example:: -.. class:: PullDOM(documentFactory=None) + from xml.dom import pulldom - :class:`xml.sax.handler.ContentHandler` implementation that ... + 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: -.. class:: DOMEventStream(stream, parser, bufsize) +* :data:`START_ELEMENT` +* :data:`END_ELEMENT` +* :data:`COMMENT` +* :data:`START_DOCUMENT` +* :data:`END_DOCUMENT` +* :data:`CHARACTERS` +* :data:`PROCESSING_INSTRUCTION` +* :data:`IGNORABLE_WHITESPACE` + +``node`` is a 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) - :class:`xml.sax.handler.ContentHandler` implementation that ... + 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 a + :class:`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 @@ -45,24 +83,37 @@ Object Model representation of a document from SAX events. 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:: DOMEventStream.getEvent() - - ... + .. method:: getEvent() -.. method:: DOMEventStream.expandNode(node) + 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 informations about its children, unless + :func:`expandNode` is called. - ... + .. method:: expandNode(node) + Expands all children of *node* into *node*. Example:: -.. method:: DOMEventStream.reset() + 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.exandNode(node) + # Following statement prints node with all its children '<p>Some text <div>and more</div></p>' + print(node.toxml()) - ... + .. method:: DOMEventStream.reset() |