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: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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The Element type is a flexible container object, designed to store hierarchical
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data structures in memory. The type can be described as a cross between a list
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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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* 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 Element or SubElement factory functions.
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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 the
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xml.etree.ElementTree.
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.. _elementtree-functions:
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.. function:: Comment([text])
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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. The comment string can be either
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an ASCII-only :class:`bytes` object or a :class:`str` object. *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 should
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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:: Element(tag[, attrib][, **extra])
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Element factory. This function returns an object implementing the standard
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Element interface. The exact class or type of that object is implementation
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dependent, but it will always be compatible with the _ElementInterface class in
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The element name, attribute names, and attribute values can be either an
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ASCII-only :class:`bytes` object or a :class:`str` object. *tag* is the
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element name. *attrib* is an optional dictionary, containing element
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attributes. *extra* contains additional attributes, given as keyword
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arguments. Returns an element instance.
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.. function:: fromstring(text)
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Parses an XML section from a string constant. Same as XML. *text* is a string
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containing XML data. Returns an Element instance.
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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])
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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 data.
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*events* is a list of events to report back. If omitted, only "end" events are
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reported. Returns an :term:`iterator` providing ``(event, elem)`` pairs.
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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])
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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 not
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given, the standard XMLTreeBuilder parser is used. Returns an ElementTree
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.. function:: ProcessingInstruction(target[, text])
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PI element factory. This factory function creates a special element that will
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be serialized as an XML processing instruction. *target* is a string containing
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the PI target. *text* is a string containing the PI contents, if given. Returns
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an element instance, representing a processing instruction.
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.. function:: SubElement(parent, tag[, attrib[, **extra]])
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Subelement factory. This function creates an element instance, and appends it
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to an existing element.
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The element name, attribute names, and attribute values can be an ASCII-only
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:class:`bytes` object or a :class:`str` object. *parent* is the parent
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element. *tag* is the subelement name. *attrib* is an optional dictionary,
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containing element attributes. *extra* contains additional attributes, given
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as keyword arguments. Returns an element instance.
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.. function:: tostring(element[, encoding])
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Generates a string representation of an XML element, including all subelements.
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*element* is an Element instance. *encoding* is the output encoding (default is
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US-ASCII). Returns an encoded string containing the XML data.
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.. function:: XML(text)
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Parses an XML section from a string constant. This function can be used to
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embed "XML literals" in Python code. *text* is a string containing XML data.
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Returns an Element instance.
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.. function:: XMLID(text)
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Parses an XML section from a string constant, and also returns a dictionary
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which maps from element id:s to elements. *text* is a string containing XML
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data. Returns a tuple containing an Element instance and a dictionary.
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.. _elementtree-element-interface:
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The Element Interface
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---------------------
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Element objects returned by Element or SubElement have the following methods
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.. attribute:: Element.tag
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A string identifying what kind of data this element represents (the element
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type, in other words).
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.. attribute:: Element.text
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The *text* attribute can be used to hold additional data associated with the
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element. As the name implies this attribute is usually a string but may be any
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application-specific object. If the element is created from an XML file the
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attribute will contain any text found between the element tags.
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.. attribute:: Element.tail
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The *tail* attribute can be used to hold additional data associated with the
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element. This attribute is usually a string but may be any application-specific
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object. If the element is created from an XML file the attribute will contain
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any text found after the element's end tag and before the next tag.
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.. attribute:: Element.attrib
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A dictionary containing the element's attributes. Note that while the *attrib*
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value is always a real mutable Python dictionary, an ElementTree implementation
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may choose to use another internal representation, and create the dictionary
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only if someone asks for it. To take advantage of such implementations, use the
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dictionary methods below whenever possible.
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The following dictionary-like methods work on the element attributes.
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.. method:: Element.clear()
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Resets an element. This function removes all subelements, clears all
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attributes, and sets the text and tail attributes to None.
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.. method:: Element.get(key[, default=None])
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Gets the element attribute named *key*.
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Returns the attribute value, or *default* if the attribute was not found.
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.. method:: Element.items()
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Returns the element attributes as a sequence of (name, value) pairs. The
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attributes are returned in an arbitrary order.
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.. method:: Element.keys()
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Returns the elements attribute names as a list. The names are returned in an
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.. method:: Element.set(key, value)
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Set the attribute *key* on the element to *value*.
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The following methods work on the element's children (subelements).
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.. method:: Element.append(subelement)
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Adds the element *subelement* to the end of this elements internal list of
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.. method:: Element.find(match)
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Finds the first subelement matching *match*. *match* may be a tag name or path.
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Returns an element instance or ``None``.
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.. method:: Element.findall(match)
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Finds all subelements matching *match*. *match* may be a tag name or path.
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Returns an iterable yielding all matching elements in document order.
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.. method:: Element.findtext(condition[, default=None])
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Finds text for the first subelement matching *condition*. *condition* may be a
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tag name or path. Returns the text content of the first matching element, or
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*default* if no element was found. Note that if the matching element has no
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text content an empty string is returned.
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.. method:: Element.getchildren()
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Returns all subelements. The elements are returned in document order.
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.. method:: Element.getiterator([tag=None])
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Creates a tree iterator with the current element as the root. The iterator
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iterates over this element and all elements below it that match the given tag.
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If tag is ``None`` or ``'*'`` then all elements are iterated over. Returns an
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iterable that provides element objects in document (depth first) order.
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.. method:: Element.insert(index, element)
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Inserts a subelement at the given position in this element.
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.. method:: Element.makeelement(tag, attrib)
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Creates a new element object of the same type as this element. Do not call this
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method, use the SubElement factory function instead.
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.. method:: Element.remove(subelement)
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Removes *subelement* from the element. Unlike the findXYZ methods this method
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compares elements based on the instance identity, not on tag value or contents.
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Element objects also support the following sequence type methods for working
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with subelements: :meth:`__delitem__`, :meth:`__getitem__`, :meth:`__setitem__`,
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Caution: Because Element objects do not define a :meth:`__bool__` method,
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elements with no subelements will test as ``False``. ::
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element = root.find('foo')
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if not element: # careful!
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print("element not found, or element has no subelements")
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print("element not found")
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.. _elementtree-elementtree-objects:
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.. class:: ElementTree([element,] [file])
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ElementTree wrapper class. This class represents an entire element hierarchy,
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and adds some extra support for serialization to and from standard XML.
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*element* is the root element. The tree is initialized with the contents of the
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.. method:: _setroot(element)
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Replaces the root element for this tree. This discards the current
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contents of the tree, and replaces it with the given element. Use with
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care. *element* is an element instance.
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.. method:: find(path)
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Finds the first toplevel element with given tag. Same as
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getroot().find(path). *path* is the element to look for. Returns the
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first matching element, or ``None`` if no element was found.
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.. method:: findall(path)
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Finds all toplevel elements with the given tag. Same as
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getroot().findall(path). *path* is the element to look for. Returns a
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list or :term:`iterator` containing all matching elements, in document
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.. method:: findtext(path[, default])
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Finds the element text for the first toplevel element with given tag.
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Same as getroot().findtext(path). *path* is the toplevel element to look
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for. *default* is the value to return if the element was not
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found. Returns the text content of the first matching element, or the
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default value no element was found. Note that if the element has is
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found, but has no text content, this method returns an empty string.
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.. method:: getiterator([tag])
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Creates and returns a tree iterator for the root element. The iterator
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loops over all elements in this tree, in section order. *tag* is the tag
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to look for (default is to return all elements)
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.. method:: getroot()
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Returns the root element for this tree.
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.. method:: parse(source[, parser])
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Loads an external XML section into this element tree. *source* is a file
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name or file object. *parser* is an optional parser instance. If not
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given, the standard XMLTreeBuilder parser is used. Returns the section
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.. method:: write(file[, encoding])
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Writes the element tree to a file, as XML. *file* is a file name, or a
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file object opened for writing. *encoding* [1]_ is the output encoding
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(default is US-ASCII).
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This is the XML file that is going to be manipulated::
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<title>Example page</title>
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<p>Moved to <a href="http://example.org/">example.org</a>
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or <a href="http://example.com/">example.com</a>.</p>
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Example of changing the attribute "target" of every link in first paragraph::
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>>> from xml.etree.ElementTree import ElementTree
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>>> tree = ElementTree()
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>>> tree.parse("index.xhtml")
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<Element html at b7d3f1ec>
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>>> p = tree.find("body/p") # Finds first occurrence of tag p in body
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<Element p at 8416e0c>
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>>> links = p.getiterator("a") # Returns list of all links
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[<Element a at b7d4f9ec>, <Element a at b7d4fb0c>]
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>>> for i in links: # Iterates through all found links
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... i.attrib["target"] = "blank"
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>>> tree.write("output.xhtml")
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.. _elementtree-qname-objects:
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.. class:: QName(text_or_uri[, tag])
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QName wrapper. This can be used to wrap a QName attribute value, in order to
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get proper namespace handling on output. *text_or_uri* is a string containing
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the QName value, in the form {uri}local, or, if the tag argument is given, the
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URI part of a QName. If *tag* is given, the first argument is interpreted as an
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URI, and this argument is interpreted as a local name. :class:`QName` instances
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.. _elementtree-treebuilder-objects:
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.. class:: TreeBuilder([element_factory])
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Generic element structure builder. This builder converts a sequence of start,
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data, and end method calls to a well-formed element structure. You can use this
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class to build an element structure using a custom XML parser, or a parser for
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some other XML-like format. The *element_factory* is called to create new
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Element instances when given.
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Flushes the parser buffers, and returns the toplevel document
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element. Returns an Element instance.
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.. method:: data(data)
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Adds text to the current element. *data* is a string. This should be
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either an ASCII-only :class:`bytes` object or a :class:`str` object.
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Closes the current element. *tag* is the element name. Returns the closed
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.. method:: start(tag, attrs)
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Opens a new element. *tag* is the element name. *attrs* is a dictionary
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containing element attributes. Returns the opened element.
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.. _elementtree-xmltreebuilder-objects:
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XMLTreeBuilder Objects
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----------------------
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.. class:: XMLTreeBuilder([html,] [target])
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Element structure builder for XML source data, based on the expat parser. *html*
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are predefined HTML entities. This flag is not supported by the current
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implementation. *target* is the target object. If omitted, the builder uses an
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instance of the standard TreeBuilder class.
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Finishes feeding data to the parser. Returns an element structure.
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.. method:: doctype(name, pubid, system)
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Handles a doctype declaration. *name* is the doctype name. *pubid* is the
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public identifier. *system* is the system identifier.
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.. method:: feed(data)
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Feeds data to the parser. *data* is encoded data.
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:meth:`XMLTreeBuilder.feed` calls *target*\'s :meth:`start` method
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for each opening tag, its :meth:`end` method for each closing tag,
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and data is processed by method :meth:`data`. :meth:`XMLTreeBuilder.close`
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calls *target*\'s method :meth:`close`.
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:class:`XMLTreeBuilder` can be used not only for building a tree structure.
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This is an example of counting the maximum depth of an XML file::
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>>> from xml.etree.ElementTree import XMLTreeBuilder
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>>> class MaxDepth: # The target object of the parser
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... def start(self, tag, attrib): # Called for each opening tag.
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... if self.depth > self.maxDepth:
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... self.maxDepth = self.depth
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... def end(self, tag): # Called for each closing tag.
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... def data(self, data):
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... pass # We do not need to do anything with data.
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... def close(self): # Called when all data has been parsed.
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... return self.maxDepth
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>>> target = MaxDepth()
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>>> parser = XMLTreeBuilder(target=target)
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>>> parser.feed(exampleXml)
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.. rubric:: Footnotes
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.. [#] The encoding string included in XML output should conform to the
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appropriate standards. For example, "UTF-8" is valid, but "UTF8" is
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not. See http://www.w3.org/TR/2006/REC-xml11-20060816/#NT-EncodingDecl
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and http://www.iana.org/assignments/character-sets.
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Doc/library/xml.etree.elementtree.rst
