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1038 lines
35 KiB
1038 lines
35 KiB
: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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.. versionadded:: 2.5
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**Source code:** :source:`Lib/xml/etree/ElementTree.py`
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--------------
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The :class:`Element` type is a flexible container object, designed to store
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hierarchical data structures in memory. The type can be described as a cross
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between a list and a dictionary.
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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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Each element has a number of properties associated with it:
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* a tag which is a string identifying what kind of data this element represents
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(the element type, in other words).
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* a number of attributes, stored in a Python dictionary.
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* a text string.
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* an optional tail string.
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* a number of child elements, stored in a Python sequence
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To create an element instance, use the :class:`Element` constructor or the
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:func:`SubElement` factory function.
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The :class:`ElementTree` class can be used to wrap an element structure, and
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convert it from and to XML.
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A C implementation of this API is available as :mod:`xml.etree.cElementTree`.
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See http://effbot.org/zone/element-index.htm for tutorials and links to other
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docs. Fredrik Lundh's page is also the location of the development version of
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the xml.etree.ElementTree.
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.. versionchanged:: 2.7
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The ElementTree API is updated to 1.3. For more information, see
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`Introducing ElementTree 1.3
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<http://effbot.org/zone/elementtree-13-intro.htm>`_.
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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 have a number of ways to import the data. Reading the file from disk::
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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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Reading the data 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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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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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``. |
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+-----------------------+------------------------------------------------------+
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| ``*`` | Selects all child elements. 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. |
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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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| ``[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:: Comment(text=None)
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Comment element factory. This factory function creates a special element
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that will be serialized as an XML comment by the standard serializer. The
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comment string can be either a bytestring or a Unicode string. *text* is a
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string containing the comment string. Returns an element instance
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representing a comment.
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.. function:: dump(elem)
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Writes an element tree or element structure to sys.stdout. This function
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should be used for debugging only.
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The exact output format is implementation dependent. In this version, it's
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written as an ordinary XML file.
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*elem* is an element tree or an individual element.
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.. function:: fromstring(text)
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Parses an XML section from a string constant. Same as :func:`XML`. *text*
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is a string containing XML data. Returns an :class:`Element` instance.
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.. function:: fromstringlist(sequence, parser=None)
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Parses an XML document from a sequence of string fragments. *sequence* is a
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list or other sequence containing XML data fragments. *parser* is an
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optional parser instance. If not given, the standard :class:`XMLParser`
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parser is used. Returns an :class:`Element` instance.
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.. versionadded:: 2.7
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.. function:: iselement(element)
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Checks if an object appears to be a valid element object. *element* is an
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element instance. Returns a true value if this is an element object.
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.. function:: iterparse(source, events=None, parser=None)
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Parses an XML section into an element tree incrementally, and reports what's
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going on to the user. *source* is a filename or file object containing XML
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data. *events* is a list of events to report back. If omitted, only "end"
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events are reported. *parser* is an optional parser instance. If not
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given, the standard :class:`XMLParser` parser is used. *parser* is not
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supported by ``cElementTree``. Returns an :term:`iterator` providing
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``(event, elem)`` pairs.
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.. note::
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:func:`iterparse` only guarantees that it has seen the ">"
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character of a starting tag when it emits a "start" event, so the
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attributes are defined, but the contents of the text and tail attributes
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are undefined at that point. The same applies to the element children;
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they may or may not be present.
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If you need a fully populated element, look for "end" events instead.
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.. function:: parse(source, parser=None)
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Parses an XML section into an element tree. *source* is a filename or file
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object containing XML data. *parser* is an optional parser instance. If
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not given, the standard :class:`XMLParser` parser is used. Returns an
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:class:`ElementTree` instance.
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.. function:: ProcessingInstruction(target, text=None)
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PI element factory. This factory function creates a special element that
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will be serialized as an XML processing instruction. *target* is a string
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containing the PI target. *text* is a string containing the PI contents, if
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given. Returns an element instance, representing a processing instruction.
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.. function:: register_namespace(prefix, uri)
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Registers a namespace prefix. The registry is global, and any existing
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mapping for either the given prefix or the namespace URI will be removed.
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*prefix* is a namespace prefix. *uri* is a namespace uri. Tags and
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attributes in this namespace will be serialized with the given prefix, if at
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all possible.
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.. versionadded:: 2.7
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.. 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")
|
|
|
|
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). *method* is either ``"xml"``,
|
|
``"html"`` or ``"text"`` (default is ``"xml"``). Returns an encoded string
|
|
containing the XML data.
|
|
|
|
|
|
.. function:: tostringlist(element, encoding="us-ascii", method="xml")
|
|
|
|
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). *method* is either ``"xml"``,
|
|
``"html"`` or ``"text"`` (default is ``"xml"``). Returns a list of encoded
|
|
strings containing the XML data. It does not guarantee any specific
|
|
sequence, except that ``"".join(tostringlist(element)) ==
|
|
tostring(element)``.
|
|
|
|
.. versionadded:: 2.7
|
|
|
|
|
|
.. 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 elements internal list
|
|
of subelements.
|
|
|
|
|
|
.. method:: extend(subelements)
|
|
|
|
Appends *subelements* from a sequence object with zero or more elements.
|
|
Raises :exc:`AssertionError` if a subelement is not a valid object.
|
|
|
|
.. versionadded:: 2.7
|
|
|
|
|
|
.. method:: find(match)
|
|
|
|
Finds the first subelement matching *match*. *match* may be a tag name
|
|
or path. Returns an element instance or ``None``.
|
|
|
|
|
|
.. method:: findall(match)
|
|
|
|
Finds all matching subelements, by tag name or path. Returns a list
|
|
containing all matching elements in document order.
|
|
|
|
|
|
.. method:: findtext(match, default=None)
|
|
|
|
Finds text for the first subelement matching *match*. *match* may be
|
|
a tag name or path. 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.
|
|
|
|
|
|
.. method:: getchildren()
|
|
|
|
.. deprecated:: 2.7
|
|
Use ``list(elem)`` or iteration.
|
|
|
|
|
|
.. method:: getiterator(tag=None)
|
|
|
|
.. deprecated:: 2.7
|
|
Use method :meth:`Element.iter` instead.
|
|
|
|
|
|
.. method:: insert(index, element)
|
|
|
|
Inserts a subelement at the given position in this 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:: 2.7
|
|
|
|
|
|
.. method:: iterfind(match)
|
|
|
|
Finds all matching subelements, by tag name or path. Returns an iterable
|
|
yielding all matching elements in document order.
|
|
|
|
.. versionadded:: 2.7
|
|
|
|
|
|
.. method:: itertext()
|
|
|
|
Creates a text iterator. The iterator loops over this element and all
|
|
subelements, in document order, and returns all inner text.
|
|
|
|
.. versionadded:: 2.7
|
|
|
|
|
|
.. 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"
|
|
|
|
|
|
.. _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)
|
|
|
|
Same as :meth:`Element.find`, starting at the root of the tree.
|
|
|
|
|
|
.. method:: findall(match)
|
|
|
|
Same as :meth:`Element.findall`, starting at the root of the tree.
|
|
|
|
|
|
.. method:: findtext(match, default=None)
|
|
|
|
Same as :meth:`Element.findtext`, starting at the root of the tree.
|
|
|
|
|
|
.. method:: getiterator(tag=None)
|
|
|
|
.. deprecated:: 2.7
|
|
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)
|
|
|
|
Finds all matching subelements, by tag name or path. Same as
|
|
getroot().iterfind(match). Returns an iterable yielding all matching
|
|
elements in document order.
|
|
|
|
.. versionadded:: 2.7
|
|
|
|
|
|
.. method:: parse(source, parser=None)
|
|
|
|
Loads an external XML section into this element tree. *source* is a file
|
|
name or file object. *parser* is an optional parser instance. If not
|
|
given, the standard XMLParser parser is used. Returns the section
|
|
root element.
|
|
|
|
|
|
.. method:: write(file, encoding="us-ascii", xml_declaration=None, \
|
|
default_namespace=None, method="xml")
|
|
|
|
Writes the element tree to a file, as XML. *file* is a file name, or a
|
|
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 (default is ``None``). *default_namespace*
|
|
sets the default XML namespace (for "xmlns"). *method* is either
|
|
``"xml"``, ``"html"`` or ``"text"`` (default is ``"xml"``). Returns an
|
|
encoded string.
|
|
|
|
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)
|
|
|
|
Generic element structure builder. This builder converts a sequence of
|
|
start, data, and end 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. The *element_factory* is called
|
|
to create new :class:`Element` instances when given.
|
|
|
|
|
|
.. 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.
|
|
|
|
|
|
In addition, a custom :class:`TreeBuilder` object can provide the
|
|
following method:
|
|
|
|
.. 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:: 2.7
|
|
|
|
|
|
.. _elementtree-xmlparser-objects:
|
|
|
|
XMLParser Objects
|
|
^^^^^^^^^^^^^^^^^
|
|
|
|
|
|
.. class:: XMLParser(html=0, target=None, encoding=None)
|
|
|
|
:class:`Element` structure builder for XML source data, based on the expat
|
|
parser. *html* are predefined HTML entities. This flag is not supported by
|
|
the current implementation. *target* is the target object. If omitted, the
|
|
builder uses an instance of the standard TreeBuilder class. *encoding* [1]_
|
|
is optional. If given, the value overrides the encoding specified in the
|
|
XML file.
|
|
|
|
|
|
.. method:: close()
|
|
|
|
Finishes feeding data to the parser. Returns an element structure.
|
|
|
|
|
|
.. method:: doctype(name, pubid, system)
|
|
|
|
.. deprecated:: 2.7
|
|
Define the :meth:`TreeBuilder.doctype` method on a custom TreeBuilder
|
|
target.
|
|
|
|
|
|
.. method:: feed(data)
|
|
|
|
Feeds data to the parser. *data* is encoded data.
|
|
|
|
:meth:`XMLParser.feed` calls *target*\'s :meth:`start` method
|
|
for each opening tag, its :meth:`end` method for each closing tag,
|
|
and data is processed by method :meth:`data`. :meth:`XMLParser.close`
|
|
calls *target*\'s method :meth:`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
|
|
|
|
|
|
.. 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.
|