| :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. |
| |
| 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 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) |
| |
| 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 |
| |
| 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 informations about its children, unless |
| :func:`expandNode` is called. |
| |
| .. method:: expandNode(node) |
| |
| Expands all children of *node* into *node*. Example:: |
| |
| 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() |
| |