/Doc/library/xml.dom.minidom.rst
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- :mod:`xml.dom.minidom` --- Lightweight DOM implementation
- =========================================================
- .. module:: xml.dom.minidom
- :synopsis: Lightweight Document Object Model (DOM) implementation.
- .. moduleauthor:: Paul Prescod <paul@prescod.net>
- .. sectionauthor:: Paul Prescod <paul@prescod.net>
- .. sectionauthor:: Martin v. Lรถwis <martin@v.loewis.de>
- .. versionadded:: 2.0
- :mod:`xml.dom.minidom` is a light-weight implementation of the Document Object
- Model interface. It is intended to be simpler than the full DOM and also
- significantly smaller.
- DOM applications typically start by parsing some XML into a DOM. With
- :mod:`xml.dom.minidom`, this is done through the parse functions::
- from xml.dom.minidom import parse, parseString
- dom1 = parse('c:\\temp\\mydata.xml') # parse an XML file by name
- datasource = open('c:\\temp\\mydata.xml')
- dom2 = parse(datasource) # parse an open file
- dom3 = parseString('<myxml>Some data<empty/> some more data</myxml>')
- The :func:`parse` function can take either a filename or an open file object.
- .. function:: parse(filename_or_file[, parser[, bufsize]])
- Return a :class:`Document` from the given input. *filename_or_file* may be
- either a file name, or a file-like object. *parser*, if given, must be a SAX2
- parser 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])
- Return a :class:`Document` that represents the *string*. This method creates a
- :class:`StringIO` object for the string and passes that on to :func:`parse`.
- Both functions return a :class:`Document` object representing the content of the
- document.
- What the :func:`parse` and :func:`parseString` functions do is connect an XML
- parser with a "DOM builder" that can accept parse events from any SAX parser and
- convert them into a DOM tree. The name of the functions are perhaps misleading,
- but are easy to grasp when learning the interfaces. The parsing of the document
- will be completed before these functions return; it's simply that these
- functions do not provide a parser implementation themselves.
- You can also create a :class:`Document` by calling a method on a "DOM
- Implementation" object. You can get this object either by calling the
- :func:`getDOMImplementation` function in the :mod:`xml.dom` package or the
- :mod:`xml.dom.minidom` module. Using the implementation from the
- :mod:`xml.dom.minidom` module will always return a :class:`Document` instance
- from the minidom implementation, while the version from :mod:`xml.dom` may
- provide an alternate implementation (this is likely if you have the `PyXML
- package <http://pyxml.sourceforge.net/>`_ installed). Once you have a
- :class:`Document`, you can add child nodes to it to populate the DOM::
- from xml.dom.minidom import getDOMImplementation
- impl = getDOMImplementation()
- newdoc = impl.createDocument(None, "some_tag", None)
- top_element = newdoc.documentElement
- text = newdoc.createTextNode('Some textual content.')
- top_element.appendChild(text)
- Once you have a DOM document object, you can access the parts of your XML
- document through its properties and methods. These properties are defined in
- the DOM specification. The main property of the document object is the
- :attr:`documentElement` property. It gives you the main element in the XML
- document: the one that holds all others. Here is an example program::
- dom3 = parseString("<myxml>Some data</myxml>")
- assert dom3.documentElement.tagName == "myxml"
- When you are finished with a DOM, you should clean it up. This is necessary
- because some versions of Python do not support garbage collection of objects
- that refer to each other in a cycle. Until this restriction is removed from all
- versions of Python, it is safest to write your code as if cycles would not be
- cleaned up.
- The way to clean up a DOM is to call its :meth:`unlink` method::
- dom1.unlink()
- dom2.unlink()
- dom3.unlink()
- :meth:`unlink` is a :mod:`xml.dom.minidom`\ -specific extension to the DOM API.
- After calling :meth:`unlink` on a node, the node and its descendants are
- essentially useless.
- .. seealso::
- `Document Object Model (DOM) Level 1 Specification <http://www.w3.org/TR/REC-DOM-Level-1/>`_
- The W3C recommendation for the DOM supported by :mod:`xml.dom.minidom`.
- .. _minidom-objects:
- DOM Objects
- -----------
- The definition of the DOM API for Python is given as part of the :mod:`xml.dom`
- module documentation. This section lists the differences between the API and
- :mod:`xml.dom.minidom`.
- .. method:: Node.unlink()
- Break internal references within the DOM so that it will be garbage collected on
- versions of Python without cyclic GC. Even when cyclic GC is available, using
- this can make large amounts of memory available sooner, so calling this on DOM
- objects as soon as they are no longer needed is good practice. This only needs
- to be called on the :class:`Document` object, but may be called on child nodes
- to discard children of that node.
- .. method:: Node.writexml(writer[, indent=""[, addindent=""[, newl=""[, encoding=""]]]])
- Write XML to the writer object. The writer should have a :meth:`write` method
- which matches that of the file object interface. The *indent* parameter is the
- indentation of the current node. The *addindent* parameter is the incremental
- indentation to use for subnodes of the current one. The *newl* parameter
- specifies the string to use to terminate newlines.
- .. versionchanged:: 2.1
- The optional keyword parameters *indent*, *addindent*, and *newl* were added to
- support pretty output.
- .. versionchanged:: 2.3
- For the :class:`Document` node, an additional keyword argument
- *encoding* can be used to specify the encoding field of the XML header.
- .. method:: Node.toxml([encoding])
- Return the XML that the DOM represents as a string.
- With no argument, the XML header does not specify an encoding, and the result is
- Unicode string if the default encoding cannot represent all characters in the
- document. Encoding this string in an encoding other than UTF-8 is likely
- incorrect, since UTF-8 is the default encoding of XML.
- With an explicit *encoding* [1]_ argument, the result is a byte string in the
- specified encoding. It is recommended that this argument is always specified. To
- avoid :exc:`UnicodeError` exceptions in case of unrepresentable text data, the
- encoding argument should be specified as "utf-8".
- .. versionchanged:: 2.3
- the *encoding* argument was introduced; see :meth:`writexml`.
- .. method:: Node.toprettyxml([indent=""[, newl=""[, encoding=""]]])
- Return a pretty-printed version of the document. *indent* specifies the
- indentation string and defaults to a tabulator; *newl* specifies the string
- emitted at the end of each line and defaults to ``\n``.
- .. versionadded:: 2.1
- .. versionchanged:: 2.3
- the encoding argument was introduced; see :meth:`writexml`.
- The following standard DOM methods have special considerations with
- :mod:`xml.dom.minidom`:
- .. method:: Node.cloneNode(deep)
- Although this method was present in the version of :mod:`xml.dom.minidom`
- packaged with Python 2.0, it was seriously broken. This has been corrected for
- subsequent releases.
- .. _dom-example:
- DOM Example
- -----------
- This example program is a fairly realistic example of a simple program. In this
- particular case, we do not take much advantage of the flexibility of the DOM.
- .. literalinclude:: ../includes/minidom-example.py
- .. _minidom-and-dom:
- minidom and the DOM standard
- ----------------------------
- The :mod:`xml.dom.minidom` module is essentially a DOM 1.0-compatible DOM with
- some DOM 2 features (primarily namespace features).
- Usage of the DOM interface in Python is straight-forward. The following mapping
- rules apply:
- * Interfaces are accessed through instance objects. Applications should not
- instantiate the classes themselves; they should use the creator functions
- available on the :class:`Document` object. Derived interfaces support all
- operations (and attributes) from the base interfaces, plus any new operations.
- * Operations are used as methods. Since the DOM uses only :keyword:`in`
- parameters, the arguments are passed in normal order (from left to right).
- There are no optional arguments. ``void`` operations return ``None``.
- * IDL attributes map to instance attributes. For compatibility with the OMG IDL
- language mapping for Python, an attribute ``foo`` can also be accessed through
- accessor methods :meth:`_get_foo` and :meth:`_set_foo`. ``readonly``
- attributes must not be changed; this is not enforced at runtime.
- * The types ``short int``, ``unsigned int``, ``unsigned long long``, and
- ``boolean`` all map to Python integer objects.
- * The type ``DOMString`` maps to Python strings. :mod:`xml.dom.minidom` supports
- either byte or Unicode strings, but will normally produce Unicode strings.
- Values of type ``DOMString`` may also be ``None`` where allowed to have the IDL
- ``null`` value by the DOM specification from the W3C.
- * ``const`` declarations map to variables in their respective scope (e.g.
- ``xml.dom.minidom.Node.PROCESSING_INSTRUCTION_NODE``); they must not be changed.
- * ``DOMException`` is currently not supported in :mod:`xml.dom.minidom`.
- Instead, :mod:`xml.dom.minidom` uses standard Python exceptions such as
- :exc:`TypeError` and :exc:`AttributeError`.
- * :class:`NodeList` objects are implemented using Python's built-in list type.
- Starting with Python 2.2, these objects provide the interface defined in the DOM
- specification, but with earlier versions of Python they do not support the
- official API. They are, however, much more "Pythonic" than the interface
- defined in the W3C recommendations.
- The following interfaces have no implementation in :mod:`xml.dom.minidom`:
- * :class:`DOMTimeStamp`
- * :class:`DocumentType` (added in Python 2.1)
- * :class:`DOMImplementation` (added in Python 2.1)
- * :class:`CharacterData`
- * :class:`CDATASection`
- * :class:`Notation`
- * :class:`Entity`
- * :class:`EntityReference`
- * :class:`DocumentFragment`
- Most of these reflect information in the XML document that is not of general
- utility to most DOM users.
- .. rubric:: Footnotes
- .. [#] The encoding string included in XML output should conform to the
- appropriate standards. For example, "UTF-8" is valid, but "UTF8" is
- not. See http://www.w3.org/TR/2006/REC-xml11-20060816/#NT-EncodingDecl
- and http://www.iana.org/assignments/character-sets .