969 lines
33 KiB
ReStructuredText
969 lines
33 KiB
ReStructuredText
:mod:`xml.etree.ElementTree` --- The ElementTree XML API
|
|
========================================================
|
|
|
|
.. module:: xml.etree.ElementTree
|
|
:synopsis: Implementation of the ElementTree API.
|
|
.. moduleauthor:: Fredrik Lundh <fredrik@pythonware.com>
|
|
|
|
The :mod:`xml.etree.ElementTree` module implements a simple and efficient API
|
|
for parsing and creating XML data.
|
|
|
|
.. versionchanged:: 3.3
|
|
This module will use a fast implementation whenever available.
|
|
The :mod:`xml.etree.cElementTree` module is deprecated.
|
|
|
|
|
|
.. warning::
|
|
|
|
The :mod:`xml.etree.ElementTree` module is not secure against
|
|
maliciously constructed data. If you need to parse untrusted or
|
|
unauthenticated data see :ref:`xml-vulnerabilities`.
|
|
|
|
Tutorial
|
|
--------
|
|
|
|
This is a short tutorial for using :mod:`xml.etree.ElementTree` (``ET`` in
|
|
short). The goal is to demonstrate some of the building blocks and basic
|
|
concepts of the module.
|
|
|
|
XML tree and elements
|
|
^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
XML is an inherently hierarchical data format, and the most natural way to
|
|
represent it is with a tree. ``ET`` has two classes for this purpose -
|
|
:class:`ElementTree` represents the whole XML document as a tree, and
|
|
:class:`Element` represents a single node in this tree. Interactions with
|
|
the whole document (reading and writing to/from files) are usually done
|
|
on the :class:`ElementTree` level. Interactions with a single XML element
|
|
and its sub-elements are done on the :class:`Element` level.
|
|
|
|
.. _elementtree-parsing-xml:
|
|
|
|
Parsing XML
|
|
^^^^^^^^^^^
|
|
|
|
We'll be using the following XML document as the sample data for this section:
|
|
|
|
.. code-block:: xml
|
|
|
|
<?xml version="1.0"?>
|
|
<data>
|
|
<country name="Liechtenstein">
|
|
<rank>1</rank>
|
|
<year>2008</year>
|
|
<gdppc>141100</gdppc>
|
|
<neighbor name="Austria" direction="E"/>
|
|
<neighbor name="Switzerland" direction="W"/>
|
|
</country>
|
|
<country name="Singapore">
|
|
<rank>4</rank>
|
|
<year>2011</year>
|
|
<gdppc>59900</gdppc>
|
|
<neighbor name="Malaysia" direction="N"/>
|
|
</country>
|
|
<country name="Panama">
|
|
<rank>68</rank>
|
|
<year>2011</year>
|
|
<gdppc>13600</gdppc>
|
|
<neighbor name="Costa Rica" direction="W"/>
|
|
<neighbor name="Colombia" direction="E"/>
|
|
</country>
|
|
</data>
|
|
|
|
We can import this data by reading from a file::
|
|
|
|
import xml.etree.ElementTree as ET
|
|
tree = ET.parse('country_data.xml')
|
|
root = tree.getroot()
|
|
|
|
Or directly from a string::
|
|
|
|
root = ET.fromstring(country_data_as_string)
|
|
|
|
:func:`fromstring` parses XML from a string directly into an :class:`Element`,
|
|
which is the root element of the parsed tree. Other parsing functions may
|
|
create an :class:`ElementTree`. Check the documentation to be sure.
|
|
|
|
As an :class:`Element`, ``root`` has a tag and a dictionary of attributes::
|
|
|
|
>>> root.tag
|
|
'data'
|
|
>>> root.attrib
|
|
{}
|
|
|
|
It also has children nodes over which we can iterate::
|
|
|
|
>>> for child in root:
|
|
... print(child.tag, child.attrib)
|
|
...
|
|
country {'name': 'Liechtenstein'}
|
|
country {'name': 'Singapore'}
|
|
country {'name': 'Panama'}
|
|
|
|
Children are nested, and we can access specific child nodes by index::
|
|
|
|
>>> root[0][1].text
|
|
'2008'
|
|
|
|
Finding interesting elements
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
:class:`Element` has some useful methods that help iterate recursively over all
|
|
the sub-tree below it (its children, their children, and so on). For example,
|
|
:meth:`Element.iter`::
|
|
|
|
>>> for neighbor in root.iter('neighbor'):
|
|
... print(neighbor.attrib)
|
|
...
|
|
{'name': 'Austria', 'direction': 'E'}
|
|
{'name': 'Switzerland', 'direction': 'W'}
|
|
{'name': 'Malaysia', 'direction': 'N'}
|
|
{'name': 'Costa Rica', 'direction': 'W'}
|
|
{'name': 'Colombia', 'direction': 'E'}
|
|
|
|
:meth:`Element.findall` finds only elements with a tag which are direct
|
|
children of the current element. :meth:`Element.find` finds the *first* child
|
|
with a particular tag, and :attr:`Element.text` accesses the element's text
|
|
content. :meth:`Element.get` accesses the element's attributes::
|
|
|
|
>>> for country in root.findall('country'):
|
|
... rank = country.find('rank').text
|
|
... name = country.get('name')
|
|
... print(name, rank)
|
|
...
|
|
Liechtenstein 1
|
|
Singapore 4
|
|
Panama 68
|
|
|
|
More sophisticated specification of which elements to look for is possible by
|
|
using :ref:`XPath <elementtree-xpath>`.
|
|
|
|
Modifying an XML File
|
|
^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
:class:`ElementTree` provides a simple way to build XML documents and write them to files.
|
|
The :meth:`ElementTree.write` method serves this purpose.
|
|
|
|
Once created, an :class:`Element` object may be manipulated by directly changing
|
|
its fields (such as :attr:`Element.text`), adding and modifying attributes
|
|
(:meth:`Element.set` method), as well as adding new children (for example
|
|
with :meth:`Element.append`).
|
|
|
|
Let's say we want to add one to each country's rank, and add an ``updated``
|
|
attribute to the rank element::
|
|
|
|
>>> for rank in root.iter('rank'):
|
|
... new_rank = int(rank.text) + 1
|
|
... rank.text = str(new_rank)
|
|
... rank.set('updated', 'yes')
|
|
...
|
|
>>> tree.write('output.xml')
|
|
|
|
Our XML now looks like this:
|
|
|
|
.. code-block:: xml
|
|
|
|
<?xml version="1.0"?>
|
|
<data>
|
|
<country name="Liechtenstein">
|
|
<rank updated="yes">2</rank>
|
|
<year>2008</year>
|
|
<gdppc>141100</gdppc>
|
|
<neighbor name="Austria" direction="E"/>
|
|
<neighbor name="Switzerland" direction="W"/>
|
|
</country>
|
|
<country name="Singapore">
|
|
<rank updated="yes">5</rank>
|
|
<year>2011</year>
|
|
<gdppc>59900</gdppc>
|
|
<neighbor name="Malaysia" direction="N"/>
|
|
</country>
|
|
<country name="Panama">
|
|
<rank updated="yes">69</rank>
|
|
<year>2011</year>
|
|
<gdppc>13600</gdppc>
|
|
<neighbor name="Costa Rica" direction="W"/>
|
|
<neighbor name="Colombia" direction="E"/>
|
|
</country>
|
|
</data>
|
|
|
|
We can remove elements using :meth:`Element.remove`. Let's say we want to
|
|
remove all countries with a rank higher than 50::
|
|
|
|
>>> for country in root.findall('country'):
|
|
... rank = int(country.find('rank').text)
|
|
... if rank > 50:
|
|
... root.remove(country)
|
|
...
|
|
>>> tree.write('output.xml')
|
|
|
|
Our XML now looks like this:
|
|
|
|
.. code-block:: xml
|
|
|
|
<?xml version="1.0"?>
|
|
<data>
|
|
<country name="Liechtenstein">
|
|
<rank updated="yes">2</rank>
|
|
<year>2008</year>
|
|
<gdppc>141100</gdppc>
|
|
<neighbor name="Austria" direction="E"/>
|
|
<neighbor name="Switzerland" direction="W"/>
|
|
</country>
|
|
<country name="Singapore">
|
|
<rank updated="yes">5</rank>
|
|
<year>2011</year>
|
|
<gdppc>59900</gdppc>
|
|
<neighbor name="Malaysia" direction="N"/>
|
|
</country>
|
|
</data>
|
|
|
|
Building XML documents
|
|
^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
The :func:`SubElement` function also provides a convenient way to create new
|
|
sub-elements for a given element::
|
|
|
|
>>> a = ET.Element('a')
|
|
>>> b = ET.SubElement(a, 'b')
|
|
>>> c = ET.SubElement(a, 'c')
|
|
>>> d = ET.SubElement(c, 'd')
|
|
>>> ET.dump(a)
|
|
<a><b /><c><d /></c></a>
|
|
|
|
Additional resources
|
|
^^^^^^^^^^^^^^^^^^^^
|
|
|
|
See http://effbot.org/zone/element-index.htm for tutorials and links to other
|
|
docs.
|
|
|
|
|
|
.. _elementtree-xpath:
|
|
|
|
XPath support
|
|
-------------
|
|
|
|
This module provides limited support for
|
|
`XPath expressions <http://www.w3.org/TR/xpath>`_ for locating elements in a
|
|
tree. The goal is to support a small subset of the abbreviated syntax; a full
|
|
XPath engine is outside the scope of the module.
|
|
|
|
Example
|
|
^^^^^^^
|
|
|
|
Here's an example that demonstrates some of the XPath capabilities of the
|
|
module. We'll be using the ``countrydata`` XML document from the
|
|
:ref:`Parsing XML <elementtree-parsing-xml>` section::
|
|
|
|
import xml.etree.ElementTree as ET
|
|
|
|
root = ET.fromstring(countrydata)
|
|
|
|
# Top-level elements
|
|
root.findall(".")
|
|
|
|
# All 'neighbor' grand-children of 'country' children of the top-level
|
|
# elements
|
|
root.findall("./country/neighbor")
|
|
|
|
# Nodes with name='Singapore' that have a 'year' child
|
|
root.findall(".//year/..[@name='Singapore']")
|
|
|
|
# 'year' nodes that are children of nodes with name='Singapore'
|
|
root.findall(".//*[@name='Singapore']/year")
|
|
|
|
# All 'neighbor' nodes that are the second child of their parent
|
|
root.findall(".//neighbor[2]")
|
|
|
|
Supported XPath syntax
|
|
^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
.. tabularcolumns:: |l|L|
|
|
|
|
+-----------------------+------------------------------------------------------+
|
|
| Syntax | Meaning |
|
|
+=======================+======================================================+
|
|
| ``tag`` | Selects all child elements with the given tag. |
|
|
| | For example, ``spam`` selects all child elements |
|
|
| | named ``spam``, ``spam/egg`` selects all |
|
|
| | grandchildren named ``egg`` in all children named |
|
|
| | ``spam``. |
|
|
+-----------------------+------------------------------------------------------+
|
|
| ``*`` | Selects all child elements. For example, ``*/egg`` |
|
|
| | selects all grandchildren named ``egg``. |
|
|
+-----------------------+------------------------------------------------------+
|
|
| ``.`` | Selects the current node. This is mostly useful |
|
|
| | at the beginning of the path, to indicate that it's |
|
|
| | a relative path. |
|
|
+-----------------------+------------------------------------------------------+
|
|
| ``//`` | Selects all subelements, on all levels beneath the |
|
|
| | current element. For example, ``.//egg`` selects |
|
|
| | all ``egg`` elements in the entire tree. |
|
|
+-----------------------+------------------------------------------------------+
|
|
| ``..`` | Selects the parent element. Returns ``None`` if the |
|
|
| | path attempts to reach the ancestors of the start |
|
|
| | element (the element ``find`` was called on). |
|
|
+-----------------------+------------------------------------------------------+
|
|
| ``[@attrib]`` | Selects all elements that have the given attribute. |
|
|
+-----------------------+------------------------------------------------------+
|
|
| ``[@attrib='value']`` | Selects all elements for which the given attribute |
|
|
| | has the given value. The value cannot contain |
|
|
| | quotes. |
|
|
+-----------------------+------------------------------------------------------+
|
|
| ``[tag]`` | Selects all elements that have a child named |
|
|
| | ``tag``. Only immediate children are supported. |
|
|
+-----------------------+------------------------------------------------------+
|
|
| ``[position]`` | Selects all elements that are located at the given |
|
|
| | position. The position can be either an integer |
|
|
| | (1 is the first position), the expression ``last()`` |
|
|
| | (for the last position), or a position relative to |
|
|
| | the last position (e.g. ``last()-1``). |
|
|
+-----------------------+------------------------------------------------------+
|
|
|
|
Predicates (expressions within square brackets) must be preceded by a tag
|
|
name, an asterisk, or another predicate. ``position`` predicates must be
|
|
preceded by a tag name.
|
|
|
|
Reference
|
|
---------
|
|
|
|
.. _elementtree-functions:
|
|
|
|
Functions
|
|
^^^^^^^^^
|
|
|
|
|
|
.. 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.
|
|
|
|
|
|
.. 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.
|
|
|
|
|
|
.. function:: fromstring(text)
|
|
|
|
Parses an XML section from a string constant. Same as :func:`XML`. *text*
|
|
is a string containing XML data. 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 list of events to report back. The
|
|
supported events are the strings ``"start"``, ``"end"``, ``"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* can only use the default
|
|
:class:`TreeBuilder` as a target. Returns an :term:`iterator` providing
|
|
``(event, elem)`` pairs.
|
|
|
|
.. 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.
|
|
|
|
|
|
.. 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.
|
|
|
|
|
|
.. 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")
|
|
|
|
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"``).
|
|
Returns an (optionally) 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). Use ``encoding="unicode"`` to
|
|
generate a Unicode string (otherwise, a bytestring is generated). *method*
|
|
is either ``"xml"``, ``"html"`` or ``"text"`` (default is ``"xml"``).
|
|
Returns a list of (optionally) encoded strings containing the XML data.
|
|
It does not guarantee any specific sequence, except that
|
|
``"".join(tostringlist(element)) == tostring(element)``.
|
|
|
|
.. versionadded:: 3.2
|
|
|
|
|
|
.. 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
|
|
|
|
The *text* attribute can be used to hold additional data associated with
|
|
the element. As the name implies this attribute is usually a string but
|
|
may be any application-specific object. If the element is created from
|
|
an XML file the attribute will contain any text found between the element
|
|
tags.
|
|
|
|
|
|
.. attribute:: tail
|
|
|
|
The *tail* attribute can be used to hold additional data associated with
|
|
the element. This attribute is usually a string but may be any
|
|
application-specific object. If the element is created from an XML file
|
|
the attribute will contain any text found after the element's end tag and
|
|
before the next tag.
|
|
|
|
|
|
.. 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.
|
|
|
|
|
|
.. 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.
|
|
|
|
|
|
.. 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.
|
|
|
|
|
|
.. method:: getchildren()
|
|
|
|
.. deprecated:: 3.2
|
|
Use ``list(elem)`` or iteration.
|
|
|
|
|
|
.. method:: getiterator(tag=None)
|
|
|
|
.. deprecated:: 3.2
|
|
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")
|
|
|
|
|
|
.. _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:: 3.2
|
|
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")
|
|
|
|
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 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.
|
|
|
|
|
|
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 an 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. *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.
|
|
|
|
.. 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:: 3.2
|
|
|
|
|
|
.. _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 :class:`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 the result of calling the
|
|
``close()`` method of the *target* passed during construction; by default,
|
|
this is the toplevel document element.
|
|
|
|
|
|
.. method:: doctype(name, pubid, system)
|
|
|
|
.. deprecated:: 3.2
|
|
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 ``start()`` method
|
|
for each opening tag, its ``end()`` method for each closing tag,
|
|
and data is processed by method ``data()``. :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
|
|
|
|
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
|
|
|
|
.. [#] The encoding string included in XML output should conform to the
|
|
appropriate standards. For example, "UTF-8" is valid, but "UTF8" is
|
|
not. See http://www.w3.org/TR/2006/REC-xml11-20060816/#NT-EncodingDecl
|
|
and http://www.iana.org/assignments/character-sets.
|