1389 lines
51 KiB
ReStructuredText
1389 lines
51 KiB
ReStructuredText
:mod:`xml.etree.ElementTree` --- The ElementTree XML API
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========================================================
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.. module:: xml.etree.ElementTree
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:synopsis: Implementation of the ElementTree API.
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.. moduleauthor:: Fredrik Lundh <fredrik@pythonware.com>
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**Source code:** :source:`Lib/xml/etree/ElementTree.py`
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--------------
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The :mod:`xml.etree.ElementTree` module implements a simple and efficient API
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for parsing and creating XML data.
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.. versionchanged:: 3.3
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This module will use a fast implementation whenever available.
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The :mod:`xml.etree.cElementTree` module is deprecated.
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.. warning::
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The :mod:`xml.etree.ElementTree` module is not secure against
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maliciously constructed data. If you need to parse untrusted or
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unauthenticated data see :ref:`xml-vulnerabilities`.
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Tutorial
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--------
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This is a short tutorial for using :mod:`xml.etree.ElementTree` (``ET`` in
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short). The goal is to demonstrate some of the building blocks and basic
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concepts of the module.
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XML tree and elements
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^^^^^^^^^^^^^^^^^^^^^
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XML is an inherently hierarchical data format, and the most natural way to
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represent it is with a tree. ``ET`` has two classes for this purpose -
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:class:`ElementTree` represents the whole XML document as a tree, and
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:class:`Element` represents a single node in this tree. Interactions with
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the whole document (reading and writing to/from files) are usually done
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on the :class:`ElementTree` level. Interactions with a single XML element
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and its sub-elements are done on the :class:`Element` level.
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.. _elementtree-parsing-xml:
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Parsing XML
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^^^^^^^^^^^
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We'll be using the following XML document as the sample data for this section:
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.. code-block:: xml
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<?xml version="1.0"?>
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<data>
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<country name="Liechtenstein">
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<rank>1</rank>
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<year>2008</year>
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<gdppc>141100</gdppc>
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<neighbor name="Austria" direction="E"/>
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<neighbor name="Switzerland" direction="W"/>
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</country>
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<country name="Singapore">
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<rank>4</rank>
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<year>2011</year>
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<gdppc>59900</gdppc>
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<neighbor name="Malaysia" direction="N"/>
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</country>
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<country name="Panama">
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<rank>68</rank>
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<year>2011</year>
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<gdppc>13600</gdppc>
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<neighbor name="Costa Rica" direction="W"/>
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<neighbor name="Colombia" direction="E"/>
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</country>
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</data>
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We can import this data by reading from a file::
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import xml.etree.ElementTree as ET
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tree = ET.parse('country_data.xml')
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root = tree.getroot()
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Or directly from a string::
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root = ET.fromstring(country_data_as_string)
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:func:`fromstring` parses XML from a string directly into an :class:`Element`,
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which is the root element of the parsed tree. Other parsing functions may
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create an :class:`ElementTree`. Check the documentation to be sure.
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As an :class:`Element`, ``root`` has a tag and a dictionary of attributes::
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>>> root.tag
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'data'
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>>> root.attrib
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{}
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It also has children nodes over which we can iterate::
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>>> for child in root:
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... print(child.tag, child.attrib)
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...
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country {'name': 'Liechtenstein'}
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country {'name': 'Singapore'}
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country {'name': 'Panama'}
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Children are nested, and we can access specific child nodes by index::
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>>> root[0][1].text
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'2008'
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.. note::
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Not all elements of the XML input will end up as elements of the
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parsed tree. Currently, this module skips over any XML comments,
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processing instructions, and document type declarations in the
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input. Nevertheless, trees built using this module's API rather
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than parsing from XML text can have comments and processing
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instructions in them; they will be included when generating XML
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output. A document type declaration may be accessed by passing a
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custom :class:`TreeBuilder` instance to the :class:`XMLParser`
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constructor.
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.. _elementtree-pull-parsing:
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Pull API for non-blocking parsing
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Most parsing functions provided by this module require the whole document
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to be read at once before returning any result. It is possible to use an
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:class:`XMLParser` and feed data into it incrementally, but it is a push API that
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calls methods on a callback target, which is too low-level and inconvenient for
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most needs. Sometimes what the user really wants is to be able to parse XML
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incrementally, without blocking operations, while enjoying the convenience of
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fully constructed :class:`Element` objects.
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The most powerful tool for doing this is :class:`XMLPullParser`. It does not
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require a blocking read to obtain the XML data, and is instead fed with data
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incrementally with :meth:`XMLPullParser.feed` calls. To get the parsed XML
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elements, call :meth:`XMLPullParser.read_events`. Here is an example::
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>>> parser = ET.XMLPullParser(['start', 'end'])
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>>> parser.feed('<mytag>sometext')
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>>> list(parser.read_events())
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[('start', <Element 'mytag' at 0x7fa66db2be58>)]
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>>> parser.feed(' more text</mytag>')
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>>> for event, elem in parser.read_events():
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... print(event)
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... print(elem.tag, 'text=', elem.text)
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...
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end
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The obvious use case is applications that operate in a non-blocking fashion
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where the XML data is being received from a socket or read incrementally from
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some storage device. In such cases, blocking reads are unacceptable.
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Because it's so flexible, :class:`XMLPullParser` can be inconvenient to use for
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simpler use-cases. If you don't mind your application blocking on reading XML
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data but would still like to have incremental parsing capabilities, take a look
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at :func:`iterparse`. It can be useful when you're reading a large XML document
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and don't want to hold it wholly in memory.
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Finding interesting elements
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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:class:`Element` has some useful methods that help iterate recursively over all
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the sub-tree below it (its children, their children, and so on). For example,
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:meth:`Element.iter`::
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>>> for neighbor in root.iter('neighbor'):
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... print(neighbor.attrib)
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...
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{'name': 'Austria', 'direction': 'E'}
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{'name': 'Switzerland', 'direction': 'W'}
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{'name': 'Malaysia', 'direction': 'N'}
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{'name': 'Costa Rica', 'direction': 'W'}
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{'name': 'Colombia', 'direction': 'E'}
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:meth:`Element.findall` finds only elements with a tag which are direct
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children of the current element. :meth:`Element.find` finds the *first* child
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with a particular tag, and :attr:`Element.text` accesses the element's text
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content. :meth:`Element.get` accesses the element's attributes::
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>>> for country in root.findall('country'):
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... rank = country.find('rank').text
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... name = country.get('name')
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... print(name, rank)
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...
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Liechtenstein 1
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Singapore 4
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Panama 68
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More sophisticated specification of which elements to look for is possible by
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using :ref:`XPath <elementtree-xpath>`.
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Modifying an XML File
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^^^^^^^^^^^^^^^^^^^^^
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:class:`ElementTree` provides a simple way to build XML documents and write them to files.
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The :meth:`ElementTree.write` method serves this purpose.
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Once created, an :class:`Element` object may be manipulated by directly changing
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its fields (such as :attr:`Element.text`), adding and modifying attributes
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(:meth:`Element.set` method), as well as adding new children (for example
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with :meth:`Element.append`).
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Let's say we want to add one to each country's rank, and add an ``updated``
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attribute to the rank element::
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>>> for rank in root.iter('rank'):
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... new_rank = int(rank.text) + 1
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... rank.text = str(new_rank)
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... rank.set('updated', 'yes')
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...
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>>> tree.write('output.xml')
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Our XML now looks like this:
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.. code-block:: xml
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<?xml version="1.0"?>
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<data>
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<country name="Liechtenstein">
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<rank updated="yes">2</rank>
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<year>2008</year>
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<gdppc>141100</gdppc>
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<neighbor name="Austria" direction="E"/>
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<neighbor name="Switzerland" direction="W"/>
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</country>
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<country name="Singapore">
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<rank updated="yes">5</rank>
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<year>2011</year>
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<gdppc>59900</gdppc>
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<neighbor name="Malaysia" direction="N"/>
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</country>
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<country name="Panama">
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<rank updated="yes">69</rank>
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<year>2011</year>
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<gdppc>13600</gdppc>
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<neighbor name="Costa Rica" direction="W"/>
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<neighbor name="Colombia" direction="E"/>
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</country>
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</data>
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We can remove elements using :meth:`Element.remove`. Let's say we want to
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remove all countries with a rank higher than 50::
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>>> for country in root.findall('country'):
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... rank = int(country.find('rank').text)
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... if rank > 50:
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... root.remove(country)
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...
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>>> tree.write('output.xml')
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Our XML now looks like this:
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.. code-block:: xml
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<?xml version="1.0"?>
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<data>
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<country name="Liechtenstein">
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<rank updated="yes">2</rank>
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<year>2008</year>
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<gdppc>141100</gdppc>
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<neighbor name="Austria" direction="E"/>
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<neighbor name="Switzerland" direction="W"/>
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</country>
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<country name="Singapore">
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<rank updated="yes">5</rank>
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<year>2011</year>
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<gdppc>59900</gdppc>
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<neighbor name="Malaysia" direction="N"/>
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</country>
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</data>
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Building XML documents
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^^^^^^^^^^^^^^^^^^^^^^
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The :func:`SubElement` function also provides a convenient way to create new
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sub-elements for a given element::
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>>> a = ET.Element('a')
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>>> b = ET.SubElement(a, 'b')
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>>> c = ET.SubElement(a, 'c')
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>>> d = ET.SubElement(c, 'd')
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>>> ET.dump(a)
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<a><b /><c><d /></c></a>
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Parsing XML with Namespaces
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^^^^^^^^^^^^^^^^^^^^^^^^^^^
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If the XML input has `namespaces
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<https://en.wikipedia.org/wiki/XML_namespace>`__, tags and attributes
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with prefixes in the form ``prefix:sometag`` get expanded to
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``{uri}sometag`` where the *prefix* is replaced by the full *URI*.
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Also, if there is a `default namespace
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<https://www.w3.org/TR/xml-names/#defaulting>`__,
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that full URI gets prepended to all of the non-prefixed tags.
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Here is an XML example that incorporates two namespaces, one with the
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prefix "fictional" and the other serving as the default namespace:
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.. code-block:: xml
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<?xml version="1.0"?>
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<actors xmlns:fictional="http://characters.example.com"
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xmlns="http://people.example.com">
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<actor>
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<name>John Cleese</name>
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<fictional:character>Lancelot</fictional:character>
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<fictional:character>Archie Leach</fictional:character>
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</actor>
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<actor>
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<name>Eric Idle</name>
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<fictional:character>Sir Robin</fictional:character>
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<fictional:character>Gunther</fictional:character>
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<fictional:character>Commander Clement</fictional:character>
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</actor>
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</actors>
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One way to search and explore this XML example is to manually add the
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URI to every tag or attribute in the xpath of a
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:meth:`~Element.find` or :meth:`~Element.findall`::
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root = fromstring(xml_text)
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for actor in root.findall('{http://people.example.com}actor'):
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name = actor.find('{http://people.example.com}name')
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print(name.text)
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for char in actor.findall('{http://characters.example.com}character'):
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print(' |-->', char.text)
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A better way to search the namespaced XML example is to create a
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dictionary with your own prefixes and use those in the search functions::
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ns = {'real_person': 'http://people.example.com',
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'role': 'http://characters.example.com'}
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for actor in root.findall('real_person:actor', ns):
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name = actor.find('real_person:name', ns)
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print(name.text)
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for char in actor.findall('role:character', ns):
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print(' |-->', char.text)
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These two approaches both output::
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John Cleese
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|--> Lancelot
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|--> Archie Leach
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Eric Idle
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|--> Sir Robin
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|--> Gunther
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|--> Commander Clement
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Additional resources
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^^^^^^^^^^^^^^^^^^^^
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See http://effbot.org/zone/element-index.htm for tutorials and links to other
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docs.
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.. _elementtree-xpath:
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XPath support
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-------------
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This module provides limited support for
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`XPath expressions <https://www.w3.org/TR/xpath>`_ for locating elements in a
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tree. The goal is to support a small subset of the abbreviated syntax; a full
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XPath engine is outside the scope of the module.
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Example
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^^^^^^^
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Here's an example that demonstrates some of the XPath capabilities of the
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module. We'll be using the ``countrydata`` XML document from the
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:ref:`Parsing XML <elementtree-parsing-xml>` section::
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import xml.etree.ElementTree as ET
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root = ET.fromstring(countrydata)
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# Top-level elements
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root.findall(".")
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# All 'neighbor' grand-children of 'country' children of the top-level
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# elements
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root.findall("./country/neighbor")
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# Nodes with name='Singapore' that have a 'year' child
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root.findall(".//year/..[@name='Singapore']")
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# 'year' nodes that are children of nodes with name='Singapore'
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root.findall(".//*[@name='Singapore']/year")
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# All 'neighbor' nodes that are the second child of their parent
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root.findall(".//neighbor[2]")
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For XML with namespaces, use the usual qualified ``{namespace}tag`` notation::
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# All dublin-core "title" tags in the document
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root.findall(".//{http://purl.org/dc/elements/1.1/}title")
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Supported XPath syntax
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^^^^^^^^^^^^^^^^^^^^^^
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.. tabularcolumns:: |l|L|
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+-----------------------+------------------------------------------------------+
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| Syntax | Meaning |
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+=======================+======================================================+
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| ``tag`` | Selects all child elements with the given tag. |
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| | For example, ``spam`` selects all child elements |
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| | named ``spam``, and ``spam/egg`` selects all |
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| | grandchildren named ``egg`` in all children named |
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| | ``spam``. ``{namespace}*`` selects all tags in the |
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| | given namespace, ``{*}spam`` selects tags named |
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| | ``spam`` in any (or no) namespace, and ``{}*`` |
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| | only selects tags that are not in a namespace. |
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| | |
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| | .. versionchanged:: 3.8 |
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| | Support for star-wildcards was added. |
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+-----------------------+------------------------------------------------------+
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| ``*`` | Selects all child elements, including comments and |
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| | processing instructions. For example, ``*/egg`` |
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| | selects all grandchildren named ``egg``. |
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+-----------------------+------------------------------------------------------+
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| ``.`` | Selects the current node. This is mostly useful |
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| | at the beginning of the path, to indicate that it's |
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| | a relative path. |
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+-----------------------+------------------------------------------------------+
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| ``//`` | Selects all subelements, on all levels beneath the |
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| | current element. For example, ``.//egg`` selects |
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| | all ``egg`` elements in the entire tree. |
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+-----------------------+------------------------------------------------------+
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| ``..`` | Selects the parent element. Returns ``None`` if the |
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| | path attempts to reach the ancestors of the start |
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| | element (the element ``find`` was called on). |
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+-----------------------+------------------------------------------------------+
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| ``[@attrib]`` | Selects all elements that have the given attribute. |
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+-----------------------+------------------------------------------------------+
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| ``[@attrib='value']`` | Selects all elements for which the given attribute |
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| | has the given value. The value cannot contain |
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| | quotes. |
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+-----------------------+------------------------------------------------------+
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| ``[tag]`` | Selects all elements that have a child named |
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| | ``tag``. Only immediate children are supported. |
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+-----------------------+------------------------------------------------------+
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| ``[.='text']`` | Selects all elements whose complete text content, |
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| | including descendants, equals the given ``text``. |
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| | |
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| | .. versionadded:: 3.7 |
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+-----------------------+------------------------------------------------------+
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| ``[tag='text']`` | Selects all elements that have a child named |
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| | ``tag`` whose complete text content, including |
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| | descendants, equals the given ``text``. |
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+-----------------------+------------------------------------------------------+
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| ``[position]`` | Selects all elements that are located at the given |
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| | position. The position can be either an integer |
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| | (1 is the first position), the expression ``last()`` |
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| | (for the last position), or a position relative to |
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| | the last position (e.g. ``last()-1``). |
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+-----------------------+------------------------------------------------------+
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Predicates (expressions within square brackets) must be preceded by a tag
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name, an asterisk, or another predicate. ``position`` predicates must be
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preceded by a tag name.
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Reference
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---------
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.. _elementtree-functions:
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Functions
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^^^^^^^^^
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.. function:: canonicalize(xml_data=None, *, out=None, from_file=None, **options)
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`C14N 2.0 <https://www.w3.org/TR/xml-c14n2/>`_ transformation function.
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Canonicalization is a way to normalise XML output in a way that allows
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byte-by-byte comparisons and digital signatures. It reduced the freedom
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that XML serializers have and instead generates a more constrained XML
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representation. The main restrictions regard the placement of namespace
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declarations, the ordering of attributes, and ignorable whitespace.
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This function takes an XML data string (*xml_data*) or a file path or
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file-like object (*from_file*) as input, converts it to the canonical
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form, and writes it out using the *out* file(-like) object, if provided,
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or returns it as a text string if not. The output file receives text,
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not bytes. It should therefore be opened in text mode with ``utf-8``
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encoding.
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Typical uses::
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xml_data = "<root>...</root>"
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print(canonicalize(xml_data))
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with open("c14n_output.xml", mode='w', encoding='utf-8') as out_file:
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canonicalize(xml_data, out=out_file)
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with open("c14n_output.xml", mode='w', encoding='utf-8') as out_file:
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canonicalize(from_file="inputfile.xml", out=out_file)
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|
|
The configuration *options* are as follows:
|
|
|
|
- *with_comments*: set to true to include comments (default: false)
|
|
- *strip_text*: set to true to strip whitespace before and after text content
|
|
(default: false)
|
|
- *rewrite_prefixes*: set to true to replace namespace prefixes by "n{number}"
|
|
(default: false)
|
|
- *qname_aware_tags*: a set of qname aware tag names in which prefixes
|
|
should be replaced in text content (default: empty)
|
|
- *qname_aware_attrs*: a set of qname aware attribute names in which prefixes
|
|
should be replaced in text content (default: empty)
|
|
- *exclude_attrs*: a set of attribute names that should not be serialised
|
|
- *exclude_tags*: a set of tag names that should not be serialised
|
|
|
|
In the option list above, "a set" refers to any collection or iterable of
|
|
strings, no ordering is expected.
|
|
|
|
.. versionadded:: 3.8
|
|
|
|
|
|
.. function:: Comment(text=None)
|
|
|
|
Comment element factory. This factory function creates a special element
|
|
that will be serialized as an XML comment by the standard serializer. The
|
|
comment string can be either a bytestring or a Unicode string. *text* is a
|
|
string containing the comment string. Returns an element instance
|
|
representing a comment.
|
|
|
|
Note that :class:`XMLParser` skips over comments in the input
|
|
instead of creating comment objects for them. An :class:`ElementTree` will
|
|
only contain comment nodes if they have been inserted into to
|
|
the tree using one of the :class:`Element` methods.
|
|
|
|
.. function:: dump(elem)
|
|
|
|
Writes an element tree or element structure to sys.stdout. This function
|
|
should be used for debugging only.
|
|
|
|
The exact output format is implementation dependent. In this version, it's
|
|
written as an ordinary XML file.
|
|
|
|
*elem* is an element tree or an individual element.
|
|
|
|
.. versionchanged:: 3.8
|
|
The :func:`dump` function now preserves the attribute order specified
|
|
by the user.
|
|
|
|
|
|
.. function:: fromstring(text, parser=None)
|
|
|
|
Parses an XML section from a string constant. Same as :func:`XML`. *text*
|
|
is a string containing XML data. *parser* is an optional parser instance.
|
|
If not given, the standard :class:`XMLParser` parser is used.
|
|
Returns an :class:`Element` instance.
|
|
|
|
|
|
.. function:: fromstringlist(sequence, parser=None)
|
|
|
|
Parses an XML document from a sequence of string fragments. *sequence* is a
|
|
list or other sequence containing XML data fragments. *parser* is an
|
|
optional parser instance. If not given, the standard :class:`XMLParser`
|
|
parser is used. Returns an :class:`Element` instance.
|
|
|
|
.. versionadded:: 3.2
|
|
|
|
|
|
.. function:: iselement(element)
|
|
|
|
Checks if an object appears to be a valid element object. *element* is an
|
|
element instance. Returns a true value if this is an element object.
|
|
|
|
|
|
.. function:: iterparse(source, events=None, parser=None)
|
|
|
|
Parses an XML section into an element tree incrementally, and reports what's
|
|
going on to the user. *source* is a filename or :term:`file object`
|
|
containing XML data. *events* is a sequence of events to report back. The
|
|
supported events are the strings ``"start"``, ``"end"``, ``"comment"``,
|
|
``"pi"``, ``"start-ns"`` and ``"end-ns"``
|
|
(the "ns" events are used to get detailed namespace
|
|
information). If *events* is omitted, only ``"end"`` events are reported.
|
|
*parser* is an optional parser instance. If not given, the standard
|
|
:class:`XMLParser` parser is used. *parser* must be a subclass of
|
|
:class:`XMLParser` and can only use the default :class:`TreeBuilder` as a
|
|
target. Returns an :term:`iterator` providing ``(event, elem)`` pairs.
|
|
|
|
Note that while :func:`iterparse` builds the tree incrementally, it issues
|
|
blocking reads on *source* (or the file it names). As such, it's unsuitable
|
|
for applications where blocking reads can't be made. For fully non-blocking
|
|
parsing, see :class:`XMLPullParser`.
|
|
|
|
.. note::
|
|
|
|
:func:`iterparse` only guarantees that it has seen the ">" character of a
|
|
starting tag when it emits a "start" event, so the attributes are defined,
|
|
but the contents of the text and tail attributes are undefined at that
|
|
point. The same applies to the element children; they may or may not be
|
|
present.
|
|
|
|
If you need a fully populated element, look for "end" events instead.
|
|
|
|
.. deprecated:: 3.4
|
|
The *parser* argument.
|
|
|
|
.. versionchanged:: 3.8
|
|
The ``comment`` and ``pi`` events were added.
|
|
|
|
|
|
.. function:: parse(source, parser=None)
|
|
|
|
Parses an XML section into an element tree. *source* is a filename or file
|
|
object containing XML data. *parser* is an optional parser instance. If
|
|
not given, the standard :class:`XMLParser` parser is used. Returns an
|
|
:class:`ElementTree` instance.
|
|
|
|
|
|
.. function:: ProcessingInstruction(target, text=None)
|
|
|
|
PI element factory. This factory function creates a special element that
|
|
will be serialized as an XML processing instruction. *target* is a string
|
|
containing the PI target. *text* is a string containing the PI contents, if
|
|
given. Returns an element instance, representing a processing instruction.
|
|
|
|
Note that :class:`XMLParser` skips over processing instructions
|
|
in the input instead of creating comment objects for them. An
|
|
:class:`ElementTree` will only contain processing instruction nodes if
|
|
they have been inserted into to the tree using one of the
|
|
:class:`Element` methods.
|
|
|
|
.. function:: register_namespace(prefix, uri)
|
|
|
|
Registers a namespace prefix. The registry is global, and any existing
|
|
mapping for either the given prefix or the namespace URI will be removed.
|
|
*prefix* is a namespace prefix. *uri* is a namespace uri. Tags and
|
|
attributes in this namespace will be serialized with the given prefix, if at
|
|
all possible.
|
|
|
|
.. versionadded:: 3.2
|
|
|
|
|
|
.. function:: SubElement(parent, tag, attrib={}, **extra)
|
|
|
|
Subelement factory. This function creates an element instance, and appends
|
|
it to an existing element.
|
|
|
|
The element name, attribute names, and attribute values can be either
|
|
bytestrings or Unicode strings. *parent* is the parent element. *tag* is
|
|
the subelement name. *attrib* is an optional dictionary, containing element
|
|
attributes. *extra* contains additional attributes, given as keyword
|
|
arguments. Returns an element instance.
|
|
|
|
|
|
.. function:: tostring(element, encoding="us-ascii", method="xml", *, \
|
|
xml_declaration=None, default_namespace=None, \
|
|
short_empty_elements=True)
|
|
|
|
Generates a string representation of an XML element, including all
|
|
subelements. *element* is an :class:`Element` instance. *encoding* [1]_ is
|
|
the output encoding (default is US-ASCII). Use ``encoding="unicode"`` to
|
|
generate a Unicode string (otherwise, a bytestring is generated). *method*
|
|
is either ``"xml"``, ``"html"`` or ``"text"`` (default is ``"xml"``).
|
|
*xml_declaration*, *default_namespace* and *short_empty_elements* has the same
|
|
meaning as in :meth:`ElementTree.write`. Returns an (optionally) encoded string
|
|
containing the XML data.
|
|
|
|
.. versionadded:: 3.4
|
|
The *short_empty_elements* parameter.
|
|
|
|
.. versionadded:: 3.8
|
|
The *xml_declaration* and *default_namespace* parameters.
|
|
|
|
.. versionchanged:: 3.8
|
|
The :func:`tostring` function now preserves the attribute order
|
|
specified by the user.
|
|
|
|
|
|
.. function:: tostringlist(element, encoding="us-ascii", method="xml", *, \
|
|
xml_declaration=None, default_namespace=None, \
|
|
short_empty_elements=True)
|
|
|
|
Generates a string representation of an XML element, including all
|
|
subelements. *element* is an :class:`Element` instance. *encoding* [1]_ is
|
|
the output encoding (default is US-ASCII). Use ``encoding="unicode"`` to
|
|
generate a Unicode string (otherwise, a bytestring is generated). *method*
|
|
is either ``"xml"``, ``"html"`` or ``"text"`` (default is ``"xml"``).
|
|
*xml_declaration*, *default_namespace* and *short_empty_elements* has the same
|
|
meaning as in :meth:`ElementTree.write`. Returns a list of (optionally) encoded
|
|
strings containing the XML data. It does not guarantee any specific sequence,
|
|
except that ``b"".join(tostringlist(element)) == tostring(element)``.
|
|
|
|
.. versionadded:: 3.2
|
|
|
|
.. versionadded:: 3.4
|
|
The *short_empty_elements* parameter.
|
|
|
|
.. versionadded:: 3.8
|
|
The *xml_declaration* and *default_namespace* parameters.
|
|
|
|
.. versionchanged:: 3.8
|
|
The :func:`tostringlist` function now preserves the attribute order
|
|
specified by the user.
|
|
|
|
|
|
.. function:: XML(text, parser=None)
|
|
|
|
Parses an XML section from a string constant. This function can be used to
|
|
embed "XML literals" in Python code. *text* is a string containing XML
|
|
data. *parser* is an optional parser instance. If not given, the standard
|
|
:class:`XMLParser` parser is used. Returns an :class:`Element` instance.
|
|
|
|
|
|
.. function:: XMLID(text, parser=None)
|
|
|
|
Parses an XML section from a string constant, and also returns a dictionary
|
|
which maps from element id:s to elements. *text* is a string containing XML
|
|
data. *parser* is an optional parser instance. If not given, the standard
|
|
:class:`XMLParser` parser is used. Returns a tuple containing an
|
|
:class:`Element` instance and a dictionary.
|
|
|
|
|
|
.. _elementtree-element-objects:
|
|
|
|
Element Objects
|
|
^^^^^^^^^^^^^^^
|
|
|
|
.. class:: Element(tag, attrib={}, **extra)
|
|
|
|
Element class. This class defines the Element interface, and provides a
|
|
reference implementation of this interface.
|
|
|
|
The element name, attribute names, and attribute values can be either
|
|
bytestrings or Unicode strings. *tag* is the element name. *attrib* is
|
|
an optional dictionary, containing element attributes. *extra* contains
|
|
additional attributes, given as keyword arguments.
|
|
|
|
|
|
.. attribute:: tag
|
|
|
|
A string identifying what kind of data this element represents (the
|
|
element type, in other words).
|
|
|
|
|
|
.. attribute:: text
|
|
tail
|
|
|
|
These attributes can be used to hold additional data associated with
|
|
the element. Their values are usually strings but may be any
|
|
application-specific object. If the element is created from
|
|
an XML file, the *text* attribute holds either the text between
|
|
the element's start tag and its first child or end tag, or ``None``, and
|
|
the *tail* attribute holds either the text between the element's
|
|
end tag and the next tag, or ``None``. For the XML data
|
|
|
|
.. code-block:: xml
|
|
|
|
<a><b>1<c>2<d/>3</c></b>4</a>
|
|
|
|
the *a* element has ``None`` for both *text* and *tail* attributes,
|
|
the *b* element has *text* ``"1"`` and *tail* ``"4"``,
|
|
the *c* element has *text* ``"2"`` and *tail* ``None``,
|
|
and the *d* element has *text* ``None`` and *tail* ``"3"``.
|
|
|
|
To collect the inner text of an element, see :meth:`itertext`, for
|
|
example ``"".join(element.itertext())``.
|
|
|
|
Applications may store arbitrary objects in these attributes.
|
|
|
|
|
|
.. attribute:: attrib
|
|
|
|
A dictionary containing the element's attributes. Note that while the
|
|
*attrib* value is always a real mutable Python dictionary, an ElementTree
|
|
implementation may choose to use another internal representation, and
|
|
create the dictionary only if someone asks for it. To take advantage of
|
|
such implementations, use the dictionary methods below whenever possible.
|
|
|
|
The following dictionary-like methods work on the element attributes.
|
|
|
|
|
|
.. method:: clear()
|
|
|
|
Resets an element. This function removes all subelements, clears all
|
|
attributes, and sets the text and tail attributes to ``None``.
|
|
|
|
|
|
.. method:: get(key, default=None)
|
|
|
|
Gets the element attribute named *key*.
|
|
|
|
Returns the attribute value, or *default* if the attribute was not found.
|
|
|
|
|
|
.. method:: items()
|
|
|
|
Returns the element attributes as a sequence of (name, value) pairs. The
|
|
attributes are returned in an arbitrary order.
|
|
|
|
|
|
.. method:: keys()
|
|
|
|
Returns the elements attribute names as a list. The names are returned
|
|
in an arbitrary order.
|
|
|
|
|
|
.. method:: set(key, value)
|
|
|
|
Set the attribute *key* on the element to *value*.
|
|
|
|
The following methods work on the element's children (subelements).
|
|
|
|
|
|
.. method:: append(subelement)
|
|
|
|
Adds the element *subelement* to the end of this element's internal list
|
|
of subelements. Raises :exc:`TypeError` if *subelement* is not an
|
|
:class:`Element`.
|
|
|
|
|
|
.. method:: extend(subelements)
|
|
|
|
Appends *subelements* from a sequence object with zero or more elements.
|
|
Raises :exc:`TypeError` if a subelement is not an :class:`Element`.
|
|
|
|
.. versionadded:: 3.2
|
|
|
|
|
|
.. method:: find(match, namespaces=None)
|
|
|
|
Finds the first subelement matching *match*. *match* may be a tag name
|
|
or a :ref:`path <elementtree-xpath>`. Returns an element instance
|
|
or ``None``. *namespaces* is an optional mapping from namespace prefix
|
|
to full name. Pass ``''`` as prefix to move all unprefixed tag names
|
|
in the expression into the given namespace.
|
|
|
|
|
|
.. method:: findall(match, namespaces=None)
|
|
|
|
Finds all matching subelements, by tag name or
|
|
:ref:`path <elementtree-xpath>`. Returns a list containing all matching
|
|
elements in document order. *namespaces* is an optional mapping from
|
|
namespace prefix to full name. Pass ``''`` as prefix to move all
|
|
unprefixed tag names in the expression into the given namespace.
|
|
|
|
|
|
.. method:: findtext(match, default=None, namespaces=None)
|
|
|
|
Finds text for the first subelement matching *match*. *match* may be
|
|
a tag name or a :ref:`path <elementtree-xpath>`. Returns the text content
|
|
of the first matching element, or *default* if no element was found.
|
|
Note that if the matching element has no text content an empty string
|
|
is returned. *namespaces* is an optional mapping from namespace prefix
|
|
to full name. Pass ``''`` as prefix to move all unprefixed tag names
|
|
in the expression into the given namespace.
|
|
|
|
|
|
.. method:: getchildren()
|
|
|
|
.. deprecated-removed:: 3.2 3.9
|
|
Use ``list(elem)`` or iteration.
|
|
|
|
|
|
.. method:: getiterator(tag=None)
|
|
|
|
.. deprecated-removed:: 3.2 3.9
|
|
Use method :meth:`Element.iter` instead.
|
|
|
|
|
|
.. method:: insert(index, subelement)
|
|
|
|
Inserts *subelement* at the given position in this element. Raises
|
|
:exc:`TypeError` if *subelement* is not an :class:`Element`.
|
|
|
|
|
|
.. method:: iter(tag=None)
|
|
|
|
Creates a tree :term:`iterator` with the current element as the root.
|
|
The iterator iterates over this element and all elements below it, in
|
|
document (depth first) order. If *tag* is not ``None`` or ``'*'``, only
|
|
elements whose tag equals *tag* are returned from the iterator. If the
|
|
tree structure is modified during iteration, the result is undefined.
|
|
|
|
.. versionadded:: 3.2
|
|
|
|
|
|
.. method:: iterfind(match, namespaces=None)
|
|
|
|
Finds all matching subelements, by tag name or
|
|
:ref:`path <elementtree-xpath>`. Returns an iterable yielding all
|
|
matching elements in document order. *namespaces* is an optional mapping
|
|
from namespace prefix to full name.
|
|
|
|
|
|
.. versionadded:: 3.2
|
|
|
|
|
|
.. method:: itertext()
|
|
|
|
Creates a text iterator. The iterator loops over this element and all
|
|
subelements, in document order, and returns all inner text.
|
|
|
|
.. versionadded:: 3.2
|
|
|
|
|
|
.. method:: makeelement(tag, attrib)
|
|
|
|
Creates a new element object of the same type as this element. Do not
|
|
call this method, use the :func:`SubElement` factory function instead.
|
|
|
|
|
|
.. method:: remove(subelement)
|
|
|
|
Removes *subelement* from the element. Unlike the find\* methods this
|
|
method compares elements based on the instance identity, not on tag value
|
|
or contents.
|
|
|
|
:class:`Element` objects also support the following sequence type methods
|
|
for working with subelements: :meth:`~object.__delitem__`,
|
|
:meth:`~object.__getitem__`, :meth:`~object.__setitem__`,
|
|
:meth:`~object.__len__`.
|
|
|
|
Caution: Elements with no subelements will test as ``False``. This behavior
|
|
will change in future versions. Use specific ``len(elem)`` or ``elem is
|
|
None`` test instead. ::
|
|
|
|
element = root.find('foo')
|
|
|
|
if not element: # careful!
|
|
print("element not found, or element has no subelements")
|
|
|
|
if element is None:
|
|
print("element not found")
|
|
|
|
Prior to Python 3.8, the serialisation order of the XML attributes of
|
|
elements was artificially made predictable by sorting the attributes by
|
|
their name. Based on the now guaranteed ordering of dicts, this arbitrary
|
|
reordering was removed in Python 3.8 to preserve the order in which
|
|
attributes were originally parsed or created by user code.
|
|
|
|
In general, user code should try not to depend on a specific ordering of
|
|
attributes, given that the `XML Information Set
|
|
<https://www.w3.org/TR/xml-infoset/>`_ explicitly excludes the attribute
|
|
order from conveying information. Code should be prepared to deal with
|
|
any ordering on input. In cases where deterministic XML output is required,
|
|
e.g. for cryptographic signing or test data sets, canonical serialisation
|
|
is available with the :func:`canonicalize` function.
|
|
|
|
In cases where canonical output is not applicable but a specific attribute
|
|
order is still desirable on output, code should aim for creating the
|
|
attributes directly in the desired order, to avoid perceptual mismatches
|
|
for readers of the code. In cases where this is difficult to achieve, a
|
|
recipe like the following can be applied prior to serialisation to enforce
|
|
an order independently from the Element creation::
|
|
|
|
def reorder_attributes(root):
|
|
for el in root.iter():
|
|
attrib = el.attrib
|
|
if len(attrib) > 1:
|
|
# adjust attribute order, e.g. by sorting
|
|
attribs = sorted(attrib.items())
|
|
attrib.clear()
|
|
attrib.update(attribs)
|
|
|
|
|
|
.. _elementtree-elementtree-objects:
|
|
|
|
ElementTree Objects
|
|
^^^^^^^^^^^^^^^^^^^
|
|
|
|
|
|
.. class:: ElementTree(element=None, file=None)
|
|
|
|
ElementTree wrapper class. This class represents an entire element
|
|
hierarchy, and adds some extra support for serialization to and from
|
|
standard XML.
|
|
|
|
*element* is the root element. The tree is initialized with the contents
|
|
of the XML *file* if given.
|
|
|
|
|
|
.. method:: _setroot(element)
|
|
|
|
Replaces the root element for this tree. This discards the current
|
|
contents of the tree, and replaces it with the given element. Use with
|
|
care. *element* is an element instance.
|
|
|
|
|
|
.. method:: find(match, namespaces=None)
|
|
|
|
Same as :meth:`Element.find`, starting at the root of the tree.
|
|
|
|
|
|
.. method:: findall(match, namespaces=None)
|
|
|
|
Same as :meth:`Element.findall`, starting at the root of the tree.
|
|
|
|
|
|
.. method:: findtext(match, default=None, namespaces=None)
|
|
|
|
Same as :meth:`Element.findtext`, starting at the root of the tree.
|
|
|
|
|
|
.. method:: getiterator(tag=None)
|
|
|
|
.. deprecated-removed:: 3.2 3.9
|
|
Use method :meth:`ElementTree.iter` instead.
|
|
|
|
|
|
.. method:: getroot()
|
|
|
|
Returns the root element for this tree.
|
|
|
|
|
|
.. method:: iter(tag=None)
|
|
|
|
Creates and returns a tree iterator for the root element. The iterator
|
|
loops over all elements in this tree, in section order. *tag* is the tag
|
|
to look for (default is to return all elements).
|
|
|
|
|
|
.. method:: iterfind(match, namespaces=None)
|
|
|
|
Same as :meth:`Element.iterfind`, starting at the root of the tree.
|
|
|
|
.. versionadded:: 3.2
|
|
|
|
|
|
.. method:: parse(source, parser=None)
|
|
|
|
Loads an external XML section into this element tree. *source* is a file
|
|
name or :term:`file object`. *parser* is an optional parser instance.
|
|
If not given, the standard :class:`XMLParser` parser is used. Returns the
|
|
section root element.
|
|
|
|
|
|
.. method:: write(file, encoding="us-ascii", xml_declaration=None, \
|
|
default_namespace=None, method="xml", *, \
|
|
short_empty_elements=True)
|
|
|
|
Writes the element tree to a file, as XML. *file* is a file name, or a
|
|
:term:`file object` opened for writing. *encoding* [1]_ is the output
|
|
encoding (default is US-ASCII).
|
|
*xml_declaration* controls if an XML declaration should be added to the
|
|
file. Use ``False`` for never, ``True`` for always, ``None``
|
|
for only if not US-ASCII or UTF-8 or Unicode (default is ``None``).
|
|
*default_namespace* sets the default XML namespace (for "xmlns").
|
|
*method* is either ``"xml"``, ``"html"`` or ``"text"`` (default is
|
|
``"xml"``).
|
|
The keyword-only *short_empty_elements* parameter controls the formatting
|
|
of elements that contain no content. If ``True`` (the default), they are
|
|
emitted as a single self-closed tag, otherwise they are emitted as a pair
|
|
of start/end tags.
|
|
|
|
The output is either a string (:class:`str`) or binary (:class:`bytes`).
|
|
This is controlled by the *encoding* argument. If *encoding* is
|
|
``"unicode"``, the output is a string; otherwise, it's binary. Note that
|
|
this may conflict with the type of *file* if it's an open
|
|
:term:`file object`; make sure you do not try to write a string to a
|
|
binary stream and vice versa.
|
|
|
|
.. versionadded:: 3.4
|
|
The *short_empty_elements* parameter.
|
|
|
|
.. versionchanged:: 3.8
|
|
The :meth:`write` method now preserves the attribute order specified
|
|
by the user.
|
|
|
|
|
|
This is the XML file that is going to be manipulated::
|
|
|
|
<html>
|
|
<head>
|
|
<title>Example page</title>
|
|
</head>
|
|
<body>
|
|
<p>Moved to <a href="http://example.org/">example.org</a>
|
|
or <a href="http://example.com/">example.com</a>.</p>
|
|
</body>
|
|
</html>
|
|
|
|
Example of changing the attribute "target" of every link in first paragraph::
|
|
|
|
>>> from xml.etree.ElementTree import ElementTree
|
|
>>> tree = ElementTree()
|
|
>>> tree.parse("index.xhtml")
|
|
<Element 'html' at 0xb77e6fac>
|
|
>>> p = tree.find("body/p") # Finds first occurrence of tag p in body
|
|
>>> p
|
|
<Element 'p' at 0xb77ec26c>
|
|
>>> links = list(p.iter("a")) # Returns list of all links
|
|
>>> links
|
|
[<Element 'a' at 0xb77ec2ac>, <Element 'a' at 0xb77ec1cc>]
|
|
>>> for i in links: # Iterates through all found links
|
|
... i.attrib["target"] = "blank"
|
|
>>> tree.write("output.xhtml")
|
|
|
|
.. _elementtree-qname-objects:
|
|
|
|
QName Objects
|
|
^^^^^^^^^^^^^
|
|
|
|
|
|
.. class:: QName(text_or_uri, tag=None)
|
|
|
|
QName wrapper. This can be used to wrap a QName attribute value, in order
|
|
to get proper namespace handling on output. *text_or_uri* is a string
|
|
containing the QName value, in the form {uri}local, or, if the tag argument
|
|
is given, the URI part of a QName. If *tag* is given, the first argument is
|
|
interpreted as a URI, and this argument is interpreted as a local name.
|
|
:class:`QName` instances are opaque.
|
|
|
|
|
|
|
|
.. _elementtree-treebuilder-objects:
|
|
|
|
TreeBuilder Objects
|
|
^^^^^^^^^^^^^^^^^^^
|
|
|
|
|
|
.. class:: TreeBuilder(element_factory=None, *, comment_factory=None, \
|
|
pi_factory=None, insert_comments=False, insert_pis=False)
|
|
|
|
Generic element structure builder. This builder converts a sequence of
|
|
start, data, end, comment and pi method calls to a well-formed element
|
|
structure. You can use this class to build an element structure using
|
|
a custom XML parser, or a parser for some other XML-like format.
|
|
|
|
*element_factory*, when given, must be a callable accepting two positional
|
|
arguments: a tag and a dict of attributes. It is expected to return a new
|
|
element instance.
|
|
|
|
The *comment_factory* and *pi_factory* functions, when given, should behave
|
|
like the :func:`Comment` and :func:`ProcessingInstruction` functions to
|
|
create comments and processing instructions. When not given, the default
|
|
factories will be used. When *insert_comments* and/or *insert_pis* is true,
|
|
comments/pis will be inserted into the tree if they appear within the root
|
|
element (but not outside of it).
|
|
|
|
.. method:: close()
|
|
|
|
Flushes the builder buffers, and returns the toplevel document
|
|
element. Returns an :class:`Element` instance.
|
|
|
|
|
|
.. method:: data(data)
|
|
|
|
Adds text to the current element. *data* is a string. This should be
|
|
either a bytestring, or a Unicode string.
|
|
|
|
|
|
.. method:: end(tag)
|
|
|
|
Closes the current element. *tag* is the element name. Returns the
|
|
closed element.
|
|
|
|
|
|
.. method:: start(tag, attrs)
|
|
|
|
Opens a new element. *tag* is the element name. *attrs* is a dictionary
|
|
containing element attributes. Returns the opened element.
|
|
|
|
|
|
.. method:: comment(text)
|
|
|
|
Creates a comment with the given *text*. If ``insert_comments`` is true,
|
|
this will also add it to the tree.
|
|
|
|
.. versionadded:: 3.8
|
|
|
|
|
|
.. method:: pi(target, text)
|
|
|
|
Creates a comment with the given *target* name and *text*. If
|
|
``insert_pis`` is true, this will also add it to the tree.
|
|
|
|
.. versionadded:: 3.8
|
|
|
|
|
|
In addition, a custom :class:`TreeBuilder` object can provide the
|
|
following methods:
|
|
|
|
.. method:: doctype(name, pubid, system)
|
|
|
|
Handles a doctype declaration. *name* is the doctype name. *pubid* is
|
|
the public identifier. *system* is the system identifier. This method
|
|
does not exist on the default :class:`TreeBuilder` class.
|
|
|
|
.. versionadded:: 3.2
|
|
|
|
.. method:: start_ns(prefix, uri)
|
|
|
|
Is called whenever the parser encounters a new namespace declaration,
|
|
before the ``start()`` callback for the opening element that defines it.
|
|
*prefix* is ``''`` for the default namespace and the declared
|
|
namespace prefix name otherwise. *uri* is the namespace URI.
|
|
|
|
.. versionadded:: 3.8
|
|
|
|
.. method:: end_ns(prefix)
|
|
|
|
Is called after the ``end()`` callback of an element that declared
|
|
a namespace prefix mapping, with the name of the *prefix* that went
|
|
out of scope.
|
|
|
|
.. versionadded:: 3.8
|
|
|
|
|
|
.. class:: C14NWriterTarget(write, *, \
|
|
with_comments=False, strip_text=False, rewrite_prefixes=False, \
|
|
qname_aware_tags=None, qname_aware_attrs=None, \
|
|
exclude_attrs=None, exclude_tags=None)
|
|
|
|
A `C14N 2.0 <https://www.w3.org/TR/xml-c14n2/>`_ writer. Arguments are the
|
|
same as for the :func:`canonicalize` function. This class does not build a
|
|
tree but translates the callback events directly into a serialised form
|
|
using the *write* function.
|
|
|
|
.. versionadded:: 3.8
|
|
|
|
|
|
.. _elementtree-xmlparser-objects:
|
|
|
|
XMLParser Objects
|
|
^^^^^^^^^^^^^^^^^
|
|
|
|
|
|
.. class:: XMLParser(*, target=None, encoding=None)
|
|
|
|
This class is the low-level building block of the module. It uses
|
|
:mod:`xml.parsers.expat` for efficient, event-based parsing of XML. It can
|
|
be fed XML data incrementally with the :meth:`feed` method, and parsing
|
|
events are translated to a push API - by invoking callbacks on the *target*
|
|
object. If *target* is omitted, the standard :class:`TreeBuilder` is used.
|
|
If *encoding* [1]_ is given, the value overrides the
|
|
encoding specified in the XML file.
|
|
|
|
.. versionchanged:: 3.8
|
|
Parameters are now :ref:`keyword-only <keyword-only_parameter>`.
|
|
The *html* argument no longer supported.
|
|
|
|
|
|
.. method:: close()
|
|
|
|
Finishes feeding data to the parser. Returns the result of calling the
|
|
``close()`` method of the *target* passed during construction; by default,
|
|
this is the toplevel document element.
|
|
|
|
|
|
.. method:: feed(data)
|
|
|
|
Feeds data to the parser. *data* is encoded data.
|
|
|
|
:meth:`XMLParser.feed` calls *target*\'s ``start(tag, attrs_dict)`` method
|
|
for each opening tag, its ``end(tag)`` method for each closing tag, and data
|
|
is processed by method ``data(data)``. For further supported callback
|
|
methods, see the :class:`TreeBuilder` class. :meth:`XMLParser.close` calls
|
|
*target*\'s method ``close()``. :class:`XMLParser` can be used not only for
|
|
building a tree structure. This is an example of counting the maximum depth
|
|
of an XML file::
|
|
|
|
>>> from xml.etree.ElementTree import XMLParser
|
|
>>> class MaxDepth: # The target object of the parser
|
|
... maxDepth = 0
|
|
... depth = 0
|
|
... def start(self, tag, attrib): # Called for each opening tag.
|
|
... self.depth += 1
|
|
... if self.depth > self.maxDepth:
|
|
... self.maxDepth = self.depth
|
|
... def end(self, tag): # Called for each closing tag.
|
|
... self.depth -= 1
|
|
... def data(self, data):
|
|
... pass # We do not need to do anything with data.
|
|
... def close(self): # Called when all data has been parsed.
|
|
... return self.maxDepth
|
|
...
|
|
>>> target = MaxDepth()
|
|
>>> parser = XMLParser(target=target)
|
|
>>> exampleXml = """
|
|
... <a>
|
|
... <b>
|
|
... </b>
|
|
... <b>
|
|
... <c>
|
|
... <d>
|
|
... </d>
|
|
... </c>
|
|
... </b>
|
|
... </a>"""
|
|
>>> parser.feed(exampleXml)
|
|
>>> parser.close()
|
|
4
|
|
|
|
|
|
.. _elementtree-xmlpullparser-objects:
|
|
|
|
XMLPullParser Objects
|
|
^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
.. class:: XMLPullParser(events=None)
|
|
|
|
A pull parser suitable for non-blocking applications. Its input-side API is
|
|
similar to that of :class:`XMLParser`, but instead of pushing calls to a
|
|
callback target, :class:`XMLPullParser` collects an internal list of parsing
|
|
events and lets the user read from it. *events* is a sequence of events to
|
|
report back. The supported events are the strings ``"start"``, ``"end"``,
|
|
``"comment"``, ``"pi"``, ``"start-ns"`` and ``"end-ns"`` (the "ns" events
|
|
are used to get detailed namespace information). If *events* is omitted,
|
|
only ``"end"`` events are reported.
|
|
|
|
.. method:: feed(data)
|
|
|
|
Feed the given bytes data to the parser.
|
|
|
|
.. method:: close()
|
|
|
|
Signal the parser that the data stream is terminated. Unlike
|
|
:meth:`XMLParser.close`, this method always returns :const:`None`.
|
|
Any events not yet retrieved when the parser is closed can still be
|
|
read with :meth:`read_events`.
|
|
|
|
.. method:: read_events()
|
|
|
|
Return an iterator over the events which have been encountered in the
|
|
data fed to the
|
|
parser. The iterator yields ``(event, elem)`` pairs, where *event* is a
|
|
string representing the type of event (e.g. ``"end"``) and *elem* is the
|
|
encountered :class:`Element` object, or other context value as follows.
|
|
|
|
* ``start``, ``end``: the current Element.
|
|
* ``comment``, ``pi``: the current comment / processing instruction
|
|
* ``start-ns``: a tuple ``(prefix, uri)`` naming the declared namespace
|
|
mapping.
|
|
* ``end-ns``: :const:`None` (this may change in a future version)
|
|
|
|
Events provided in a previous call to :meth:`read_events` will not be
|
|
yielded again. Events are consumed from the internal queue only when
|
|
they are retrieved from the iterator, so multiple readers iterating in
|
|
parallel over iterators obtained from :meth:`read_events` will have
|
|
unpredictable results.
|
|
|
|
.. note::
|
|
|
|
:class:`XMLPullParser` only guarantees that it has seen the ">"
|
|
character of a starting tag when it emits a "start" event, so the
|
|
attributes are defined, but the contents of the text and tail attributes
|
|
are undefined at that point. The same applies to the element children;
|
|
they may or may not be present.
|
|
|
|
If you need a fully populated element, look for "end" events instead.
|
|
|
|
.. versionadded:: 3.4
|
|
|
|
.. versionchanged:: 3.8
|
|
The ``comment`` and ``pi`` events were added.
|
|
|
|
|
|
Exceptions
|
|
^^^^^^^^^^
|
|
|
|
.. class:: ParseError
|
|
|
|
XML parse error, raised by the various parsing methods in this module when
|
|
parsing fails. The string representation of an instance of this exception
|
|
will contain a user-friendly error message. In addition, it will have
|
|
the following attributes available:
|
|
|
|
.. attribute:: code
|
|
|
|
A numeric error code from the expat parser. See the documentation of
|
|
:mod:`xml.parsers.expat` for the list of error codes and their meanings.
|
|
|
|
.. attribute:: position
|
|
|
|
A tuple of *line*, *column* numbers, specifying where the error occurred.
|
|
|
|
.. rubric:: Footnotes
|
|
|
|
.. [1] The encoding string included in XML output should conform to the
|
|
appropriate standards. For example, "UTF-8" is valid, but "UTF8" is
|
|
not. See https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-EncodingDecl
|
|
and https://www.iana.org/assignments/character-sets/character-sets.xhtml.
|