cpython/Doc/library/xml.dom.minidom.rst

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:mod:`xml.dom.minidom` --- Minimal DOM implementation
=====================================================
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.. module:: xml.dom.minidom
:synopsis: Minimal Document Object Model (DOM) implementation.
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.. moduleauthor:: Paul Prescod <paul@prescod.net>
.. sectionauthor:: Paul Prescod <paul@prescod.net>
.. sectionauthor:: Martin v. Löwis <martin@v.loewis.de>
2011-02-10 04:09:36 -04:00
**Source code:** :source:`Lib/xml/dom/minidom.py`
--------------
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:mod:`xml.dom.minidom` is a minimal implementation of the Document Object
Model interface, with an API similar to that in other languages. It is intended
to be simpler than the full DOM and also significantly smaller. Users who are
not already proficient with the DOM should consider using the
:mod:`xml.etree.ElementTree` module for their XML processing instead
.. warning::
The :mod:`xml.dom.minidom` module is not secure against
maliciously constructed data. If you need to parse untrusted or
unauthenticated data see :ref:`xml-vulnerabilities`.
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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=None, bufsize=None)
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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=None)
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Return a :class:`Document` that represents the *string*. This method creates a
:class:`io.StringIO` object for the string and passes that on to :func:`parse`.
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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. Once you have a :class:`Document`, you
can add child nodes to it to populate the DOM::
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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"
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When you are finished with a DOM tree, you may optionally call the
:meth:`unlink` method to encourage early cleanup of the now-unneeded
objects. :meth:`unlink` is a :mod:`xml.dom.minidom`\ -specific
extension to the DOM API that renders the node and its descendants are
essentially useless. Otherwise, Python's garbage collector will
eventually take care of the objects in the tree.
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.. 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.
You can avoid calling this method explicitly by using the :keyword:`with`
statement. The following code will automatically unlink *dom* when the
:keyword:`with` block is exited::
with xml.dom.minidom.parse(datasource) as dom:
... # Work with dom.
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.. method:: Node.writexml(writer, indent="", addindent="", newl="")
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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.
For the :class:`Document` node, an additional keyword argument *encoding* can
be used to specify the encoding field of the XML header.
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.. method:: Node.toxml(encoding=None)
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Return a string or byte string containing the XML represented by
the DOM node.
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With an explicit *encoding* [1]_ argument, the result is a byte
string in the specified encoding.
With no *encoding* argument, the result is a Unicode string, and the
XML declaration in the resulting string does not specify an
encoding. Encoding this string in an encoding other than UTF-8 is
likely incorrect, since UTF-8 is the default encoding of XML.
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.. method:: Node.toprettyxml(indent="", newl="", encoding="")
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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``.
The *encoding* argument behaves like the corresponding argument of
:meth:`toxml`.
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.. _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``.
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* 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``
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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 bytes or strings, but will normally produce strings.
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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.
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``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.
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.
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The following interfaces have no implementation in :mod:`xml.dom.minidom`:
* :class:`DOMTimeStamp`
* :class:`DocumentType`
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* :class:`DOMImplementation`
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* :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.
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Tim Peters said it wasn't a real issue anyway, and it no longer causes test failures. Fixes issue #1779871. ........ r61439 | martin.v.loewis | 2008-03-17 17:31:57 +0100 (Mo, 17 Mär 2008) | 2 lines Add Trent Nelson. ........ r61444 | travis.oliphant | 2008-03-17 18:36:12 +0100 (Mo, 17 Mär 2008) | 1 line Add necessary headers to back-port new buffer protocol to Python 2.6 ........ r61449 | gregory.p.smith | 2008-03-17 19:48:05 +0100 (Mo, 17 Mär 2008) | 8 lines Force zlib.crc32 and zlib.adler32 to return a signed integer on all platforms regardless of the native sizeof(long) used in the integer object. This somewhat odd behavior of returning a signed is maintained in 2.x for compatibility reasons of always returning an integer rather than a long object. Fixes Issue1202 for Python 2.6 ........ r61450 | neal.norwitz | 2008-03-17 20:02:45 +0100 (Mo, 17 Mär 2008) | 3 lines Use a buffer large enough to ensure we don't overrun, even if the value is outside the range we expect. ........ r61453 | steven.bethard | 2008-03-17 20:33:11 +0100 (Mo, 17 Mär 2008) | 1 line Document unicode.isnumeric() and unicode.isdecimal() (issue2326) ........ r61458 | neal.norwitz | 2008-03-17 21:22:43 +0100 (Mo, 17 Mär 2008) | 5 lines Issue 2321: reduce memory usage (increase the memory that is returned to the system) by using pymalloc for the data of unicode objects. Will backport. ........ r61465 | martin.v.loewis | 2008-03-17 22:55:30 +0100 (Mo, 17 Mär 2008) | 2 lines Add David Wolever. ........ r61468 | gregory.p.smith | 2008-03-18 01:20:01 +0100 (Di, 18 Mär 2008) | 3 lines Fix the IOError message text when opening a file with an invalid filename. Error reported by Ilan Schnell. ........ r61471 | brett.cannon | 2008-03-18 02:00:07 +0100 (Di, 18 Mär 2008) | 2 lines Convert test_strftime, test_getargs, and test_pep247 to use unittest. ........ r61472 | jeffrey.yasskin | 2008-03-18 02:09:59 +0100 (Di, 18 Mär 2008) | 2 lines Fix build on platforms that don't have intptr_t. Patch by Joseph Armbruster. ........ r61473 | brett.cannon | 2008-03-18 02:50:25 +0100 (Di, 18 Mär 2008) | 2 lines Convert test_dummy_threading and test_dbm to unittest. ........ r61474 | brett.cannon | 2008-03-18 02:58:56 +0100 (Di, 18 Mär 2008) | 2 lines Move test_extcall to doctest. ........ r61480 | brett.cannon | 2008-03-18 04:46:22 +0100 (Di, 18 Mär 2008) | 2 lines test_errno was a no-op test; now it actually tests things and uses unittest. ........ r61483 | brett.cannon | 2008-03-18 05:09:00 +0100 (Di, 18 Mär 2008) | 3 lines Remove our implementation of memmove() and strerror(); both are in the C89 standard library. ........ r61484 | brett.cannon | 2008-03-18 05:16:06 +0100 (Di, 18 Mär 2008) | 2 lines The output directory for tests that compare against stdout is now gone! ........ r61488 | jeffrey.yasskin | 2008-03-18 05:29:35 +0100 (Di, 18 Mär 2008) | 2 lines Block the "socket.ssl() is deprecated" warning from test_socket_ssl. ........ r61495 | jeffrey.yasskin | 2008-03-18 05:56:06 +0100 (Di, 18 Mär 2008) | 4 lines Speed test_thread up from 51.328s to 0.081s by reducing its sleep times. We still sleep at all to make it likely that all threads are active at the same time. ........ r61496 | jeffrey.yasskin | 2008-03-18 06:12:41 +0100 (Di, 18 Mär 2008) | 4 lines Speed up test_dict by about 10x by only checking selected dict literal sizes, instead of every integer from 0 to 400. Exhaustive testing wastes time without providing enough more assurance that the code is correct. ........ r61498 | neal.norwitz | 2008-03-18 06:20:29 +0100 (Di, 18 Mär 2008) | 1 line Try increasing the timeout to reduce the flakiness of this test. ........ r61503 | brett.cannon | 2008-03-18 06:43:04 +0100 (Di, 18 Mär 2008) | 2 lines Improve the error message for a test that failed on the S-390 Debian buildbot. ........ r61504 | jeffrey.yasskin | 2008-03-18 06:45:40 +0100 (Di, 18 Mär 2008) | 3 lines Add a -S/--slow flag to regrtest to have it print the 10 slowest tests with their times. ........ r61507 | neal.norwitz | 2008-03-18 07:03:46 +0100 (Di, 18 Mär 2008) | 1 line Add some info to the failure messages ........ r61509 | trent.nelson | 2008-03-18 08:02:12 +0100 (Di, 18 Mär 2008) | 1 line Issue 2286: bump up the stack size of the 64-bit debug python_d.exe to 2100000. The default value of 200000 causes a stack overflow at 1965 iterations of r_object() in marshal.c, 35 iterations before the 2000 limit enforced by MAX_MARSHAL_STACK_DEPTH. ........ r61510 | trent.nelson | 2008-03-18 08:32:47 +0100 (Di, 18 Mär 2008) | 5 lines The behaviour of winsound.Beep() seems to differ between different versions of Windows when there's either: a) no sound card entirely b) legacy beep driver has been disabled c) the legacy beep driver has been uninstalled Sometimes RuntimeErrors are raised, sometimes they're not. If _have_soundcard() returns False, don't expect winsound.Beep() to raise a RuntimeError, as this clearly isn't the case, as demonstrated by the various Win32 XP buildbots. ........ r61515 | martin.v.loewis | 2008-03-18 13:20:15 +0100 (Di, 18 Mär 2008) | 2 lines norwitz-amd64 (gentoo) has EREMOTEIO. ........ r61516 | martin.v.loewis | 2008-03-18 13:45:37 +0100 (Di, 18 Mär 2008) | 2 lines Add more Linux error codes. ........ r61517 | martin.v.loewis | 2008-03-18 14:05:03 +0100 (Di, 18 Mär 2008) | 2 lines Add WSA errors. ........ r61518 | martin.v.loewis | 2008-03-18 14:16:05 +0100 (Di, 18 Mär 2008) | 2 lines Note that the stderr output of the test is intentional. ........
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.. rubric:: Footnotes
.. [#] The encoding name included in the XML output should conform to
the appropriate standards. For example, "UTF-8" is valid, but
"UTF8" is not valid in an XML document's declaration, even though
Python accepts it as an encoding name.
See http://www.w3.org/TR/2006/REC-xml11-20060816/#NT-EncodingDecl
and http://www.iana.org/assignments/character-sets\ .