| :mod:`xml.etree.ElementTree` --- The ElementTree XML API |
| ======================================================== |
| |
| .. module:: xml.etree.ElementTree |
| :synopsis: Implementation of the ElementTree API. |
| |
| .. moduleauthor:: Fredrik Lundh <fredrik@pythonware.com> |
| |
| **Source code:** :source:`Lib/xml/etree/ElementTree.py` |
| |
| -------------- |
| |
| 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' |
| |
| |
| .. note:: |
| |
| Not all elements of the XML input will end up as elements of the |
| parsed tree. Currently, this module skips over any XML comments, |
| processing instructions, and document type declarations in the |
| input. Nevertheless, trees built using this module's API rather |
| than parsing from XML text can have comments and processing |
| instructions in them; they will be included when generating XML |
| output. A document type declaration may be accessed by passing a |
| custom :class:`TreeBuilder` instance to the :class:`XMLParser` |
| constructor. |
| |
| |
| .. _elementtree-pull-parsing: |
| |
| Pull API for non-blocking parsing |
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| |
| Most parsing functions provided by this module require the whole document |
| to be read at once before returning any result. It is possible to use an |
| :class:`XMLParser` and feed data into it incrementally, but it is a push API that |
| calls methods on a callback target, which is too low-level and inconvenient for |
| most needs. Sometimes what the user really wants is to be able to parse XML |
| incrementally, without blocking operations, while enjoying the convenience of |
| fully constructed :class:`Element` objects. |
| |
| The most powerful tool for doing this is :class:`XMLPullParser`. It does not |
| require a blocking read to obtain the XML data, and is instead fed with data |
| incrementally with :meth:`XMLPullParser.feed` calls. To get the parsed XML |
| elements, call :meth:`XMLPullParser.read_events`. Here is an example:: |
| |
| >>> parser = ET.XMLPullParser(['start', 'end']) |
| >>> parser.feed('<mytag>sometext') |
| >>> list(parser.read_events()) |
| [('start', <Element 'mytag' at 0x7fa66db2be58>)] |
| >>> parser.feed(' more text</mytag>') |
| >>> for event, elem in parser.read_events(): |
| ... print(event) |
| ... print(elem.tag, 'text=', elem.text) |
| ... |
| end |
| |
| The obvious use case is applications that operate in a non-blocking fashion |
| where the XML data is being received from a socket or read incrementally from |
| some storage device. In such cases, blocking reads are unacceptable. |
| |
| Because it's so flexible, :class:`XMLPullParser` can be inconvenient to use for |
| simpler use-cases. If you don't mind your application blocking on reading XML |
| data but would still like to have incremental parsing capabilities, take a look |
| at :func:`iterparse`. It can be useful when you're reading a large XML document |
| and don't want to hold it wholly in memory. |
| |
| 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> |
| |
| Parsing XML with Namespaces |
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| |
| If the XML input has `namespaces |
| <https://en.wikipedia.org/wiki/XML_namespace>`__, tags and attributes |
| with prefixes in the form ``prefix:sometag`` get expanded to |
| ``{uri}sometag`` where the *prefix* is replaced by the full *URI*. |
| Also, if there is a `default namespace |
| <https://www.w3.org/TR/2006/REC-xml-names-20060816/#defaulting>`__, |
| that full URI gets prepended to all of the non-prefixed tags. |
| |
| Here is an XML example that incorporates two namespaces, one with the |
| prefix "fictional" and the other serving as the default namespace: |
| |
| .. code-block:: xml |
| |
| <?xml version="1.0"?> |
| <actors xmlns:fictional="http://characters.example.com" |
| xmlns="http://people.example.com"> |
| <actor> |
| <name>John Cleese</name> |
| <fictional:character>Lancelot</fictional:character> |
| <fictional:character>Archie Leach</fictional:character> |
| </actor> |
| <actor> |
| <name>Eric Idle</name> |
| <fictional:character>Sir Robin</fictional:character> |
| <fictional:character>Gunther</fictional:character> |
| <fictional:character>Commander Clement</fictional:character> |
| </actor> |
| </actors> |
| |
| One way to search and explore this XML example is to manually add the |
| URI to every tag or attribute in the xpath of a |
| :meth:`~Element.find` or :meth:`~Element.findall`:: |
| |
| root = fromstring(xml_text) |
| for actor in root.findall('{http://people.example.com}actor'): |
| name = actor.find('{http://people.example.com}name') |
| print(name.text) |
| for char in actor.findall('{http://characters.example.com}character'): |
| print(' |-->', char.text) |
| |
| A better way to search the namespaced XML example is to create a |
| dictionary with your own prefixes and use those in the search functions:: |
| |
| ns = {'real_person': 'http://people.example.com', |
| 'role': 'http://characters.example.com'} |
| |
| for actor in root.findall('real_person:actor', ns): |
| name = actor.find('real_person:name', ns) |
| print(name.text) |
| for char in actor.findall('role:character', ns): |
| print(' |-->', char.text) |
| |
| These two approaches both output:: |
| |
| John Cleese |
| |--> Lancelot |
| |--> Archie Leach |
| Eric Idle |
| |--> Sir Robin |
| |--> Gunther |
| |--> Commander Clement |
| |
| |
| 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 <https://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``, and ``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. | |
| +-----------------------+------------------------------------------------------+ |
| | ``[tag='text']`` | Selects all elements that have a child named | |
| | | ``tag`` whose complete text content, including | |
| | | descendants, equals the given ``text``. | |
| +-----------------------+------------------------------------------------------+ |
| | ``[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. |
| |
| 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. |
| |
| |
| .. 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 sequence 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* 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. |
| |
| .. 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", *, \ |
| 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"``). |
| *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. |
| |
| |
| .. function:: tostringlist(element, encoding="us-ascii", method="xml", *, \ |
| 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"``). |
| *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. |
| |
| |
| .. 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. |
| |
| |
| .. 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", *, \ |
| 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. |
| |
| |
| 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. *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) |
| |
| 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. |
| The *html* argument was historically used for backwards compatibility and is |
| now deprecated. If *encoding* [1]_ is given, the value overrides the |
| encoding specified in the XML file. |
| |
| .. deprecated:: 3.4 |
| The *html* argument. The remaining arguments should be passed via |
| keyword to prepare for the removal of the *html* argument. |
| |
| .. 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(tag, attrs_dict)`` method |
| for each opening tag, its ``end(tag)`` method for each closing tag, and data |
| is processed by method ``data(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 |
| |
| |
| .. _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"``, |
| ``"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. |
| |
| 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 |
| |
| 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 https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-EncodingDecl |
| and https://www.iana.org/assignments/character-sets/character-sets.xhtml. |
