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authorGeorg Brandl <georg@python.org>2007-08-15 14:28:01 (GMT)
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+
+:mod:`xml.etree.ElementTree` --- The ElementTree XML API
+========================================================
+
+.. module:: xml.etree.ElementTree
+ :synopsis: Implementation of the ElementTree API.
+.. moduleauthor:: Fredrik Lundh <fredrik@pythonware.com>
+
+
+.. versionadded:: 2.5
+
+The Element type is a flexible container object, designed to store hierarchical
+data structures in memory. The type can be described as a cross between a list
+and a dictionary.
+
+Each element has a number of properties associated with it:
+
+* a tag which is a string identifying what kind of data this element represents
+ (the element type, in other words).
+
+* a number of attributes, stored in a Python dictionary.
+
+* a text string.
+
+* an optional tail string.
+
+* a number of child elements, stored in a Python sequence
+
+To create an element instance, use the Element or SubElement factory functions.
+
+The :class:`ElementTree` class can be used to wrap an element structure, and
+convert it from and to XML.
+
+A C implementation of this API is available as :mod:`xml.etree.cElementTree`.
+
+
+.. _elementtree-functions:
+
+Functions
+---------
+
+
+.. function:: Comment([text])
+
+ Comment element factory. This factory function creates a special element that
+ will be serialized as an XML comment. The comment string can be either an 8-bit
+ ASCII string 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:: Element(tag[, attrib][, **extra])
+
+ Element factory. This function returns an object implementing the standard
+ Element interface. The exact class or type of that object is implementation
+ dependent, but it will always be compatible with the _ElementInterface class in
+ this module.
+
+ The element name, attribute names, and attribute values can be either 8-bit
+ ASCII strings or Unicode strings. *tag* is the element name. *attrib* is an
+ optional dictionary, containing element attributes. *extra* contains additional
+ attributes, given as keyword arguments. Returns an element instance.
+
+
+.. function:: fromstring(text)
+
+ Parses an XML section from a string constant. Same as XML. *text* is a string
+ containing XML data. Returns an Element instance.
+
+
+.. 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])
+
+ Parses an XML section into an element tree incrementally, and reports what's
+ going on to the user. *source* is a filename or file object containing XML data.
+ *events* is a list of events to report back. If omitted, only "end" events are
+ reported. Returns an iterator providing ``(event, elem)`` pairs.
+
+
+.. function:: parse(source[, parser])
+
+ 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 XMLTreeBuilder parser is used. Returns an ElementTree
+ instance.
+
+
+.. function:: ProcessingInstruction(target[, text])
+
+ 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:: 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 8-bit
+ ASCII strings 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])
+
+ Generates a string representation of an XML element, including all subelements.
+ *element* is an Element instance. *encoding* is the output encoding (default is
+ US-ASCII). Returns an encoded string containing the XML data.
+
+
+.. function:: XML(text)
+
+ 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.
+ Returns an Element instance.
+
+
+.. function:: XMLID(text)
+
+ 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. Returns a tuple containing an Element instance and a dictionary.
+
+
+.. _elementtree-element-interface:
+
+The Element Interface
+---------------------
+
+Element objects returned by Element or SubElement have the following methods
+and attributes.
+
+
+.. attribute:: Element.tag
+
+ A string identifying what kind of data this element represents (the element
+ type, in other words).
+
+
+.. attribute:: Element.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:: Element.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:: Element.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:: Element.clear()
+
+ Resets an element. This function removes all subelements, clears all
+ attributes, and sets the text and tail attributes to None.
+
+
+.. method:: Element.get(key[, default=None])
+
+ Gets the element attribute named *key*.
+
+ Returns the attribute value, or *default* if the attribute was not found.
+
+
+.. method:: Element.items()
+
+ Returns the element attributes as a sequence of (name, value) pairs. The
+ attributes are returned in an arbitrary order.
+
+
+.. method:: Element.keys()
+
+ Returns the elements attribute names as a list. The names are returned in an
+ arbitrary order.
+
+
+.. method:: Element.set(key, value)
+
+ Set the attribute *key* on the element to *value*.
+
+The following methods work on the element's children (subelements).
+
+
+.. method:: Element.append(subelement)
+
+ Adds the element *subelement* to the end of this elements internal list of
+ subelements.
+
+
+.. method:: Element.find(match)
+
+ Finds the first subelement matching *match*. *match* may be a tag name or path.
+ Returns an element instance or ``None``.
+
+
+.. method:: Element.findall(match)
+
+ Finds all subelements matching *match*. *match* may be a tag name or path.
+ Returns an iterable yielding all matching elements in document order.
+
+
+.. method:: Element.findtext(condition[, default=None])
+
+ Finds text for the first subelement matching *condition*. *condition* may be a
+ tag name or path. Returns the text content of the first matching element, or
+ *default* if no element was found. Note that if the matching element has no
+ text content an empty string is returned.
+
+
+.. method:: Element.getchildren()
+
+ Returns all subelements. The elements are returned in document order.
+
+
+.. method:: Element.getiterator([tag=None])
+
+ Creates a tree iterator with the current element as the root. The iterator
+ iterates over this element and all elements below it that match the given tag.
+ If tag is ``None`` or ``'*'`` then all elements are iterated over. Returns an
+ iterable that provides element objects in document (depth first) order.
+
+
+.. method:: Element.insert(index, element)
+
+ Inserts a subelement at the given position in this element.
+
+
+.. method:: Element.makeelement(tag, attrib)
+
+ Creates a new element object of the same type as this element. Do not call this
+ method, use the SubElement factory function instead.
+
+
+.. method:: Element.remove(subelement)
+
+ Removes *subelement* from the element. Unlike the findXYZ methods this method
+ compares elements based on the instance identity, not on tag value or contents.
+
+Element objects also support the following sequence type methods for working
+with subelements: :meth:`__delitem__`, :meth:`__getitem__`, :meth:`__setitem__`,
+:meth:`__len__`.
+
+Caution: Because Element objects do not define a :meth:`__nonzero__` method,
+elements with no subelements will test as ``False``. ::
+
+ 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,] [file])
+
+ 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:: ElementTree._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:: ElementTree.find(path)
+
+ Finds the first toplevel element with given tag. Same as getroot().find(path).
+ *path* is the element to look for. Returns the first matching element, or
+ ``None`` if no element was found.
+
+
+.. method:: ElementTree.findall(path)
+
+ Finds all toplevel elements with the given tag. Same as getroot().findall(path).
+ *path* is the element to look for. Returns a list or iterator containing all
+ matching elements, in document order.
+
+
+.. method:: ElementTree.findtext(path[, default])
+
+ Finds the element text for the first toplevel element with given tag. Same as
+ getroot().findtext(path). *path* is the toplevel element to look for. *default*
+ is the value to return if the element was not found. Returns the text content of
+ the first matching element, or the default value no element was found. Note
+ that if the element has is found, but has no text content, this method returns
+ an empty string.
+
+
+.. method:: ElementTree.getiterator([tag])
+
+ 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:: ElementTree.getroot()
+
+ Returns the root element for this tree.
+
+
+.. method:: ElementTree.parse(source[, parser])
+
+ Loads an external XML section into this element tree. *source* is a file name or
+ file object. *parser* is an optional parser instance. If not given, the
+ standard XMLTreeBuilder parser is used. Returns the section root element.
+
+
+.. method:: ElementTree.write(file[, encoding])
+
+ Writes the element tree to a file, as XML. *file* is a file name, or a file
+ object opened for writing. *encoding* is the output encoding (default is
+ US-ASCII).
+
+
+.. _elementtree-qname-objects:
+
+QName Objects
+-------------
+
+
+.. class:: QName(text_or_uri[, tag])
+
+ 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])
+
+ Generic element structure builder. This builder converts a sequence of start,
+ data, and end method calls to a well-formed element structure. You can use this
+ class to build an element structure using a custom XML parser, or a parser for
+ some other XML-like format. The *element_factory* is called to create new
+ Element instances when given.
+
+
+.. method:: TreeBuilder.close()
+
+ Flushes the parser buffers, and returns the toplevel documen element. Returns an
+ Element instance.
+
+
+.. method:: TreeBuilder.data(data)
+
+ Adds text to the current element. *data* is a string. This should be either an
+ 8-bit string containing ASCII text, or a Unicode string.
+
+
+.. method:: TreeBuilder.end(tag)
+
+ Closes the current element. *tag* is the element name. Returns the closed
+ element.
+
+
+.. method:: TreeBuilder.start(tag, attrs)
+
+ Opens a new element. *tag* is the element name. *attrs* is a dictionary
+ containing element attributes. Returns the opened element.
+
+
+.. _elementtree-xmltreebuilder-objects:
+
+XMLTreeBuilder Objects
+----------------------
+
+
+.. class:: XMLTreeBuilder([html,] [target])
+
+ Element structure builder for XML source data, based on the expat parser. *html*
+ are predefined HTML entities. This flag is not supported by the current
+ implementation. *target* is the target object. If omitted, the builder uses an
+ instance of the standard TreeBuilder class.
+
+
+.. method:: XMLTreeBuilder.close()
+
+ Finishes feeding data to the parser. Returns an element structure.
+
+
+.. method:: XMLTreeBuilder.doctype(name, pubid, system)
+
+ Handles a doctype declaration. *name* is the doctype name. *pubid* is the public
+ identifier. *system* is the system identifier.
+
+
+.. method:: XMLTreeBuilder.feed(data)
+
+ Feeds data to the parser. *data* is encoded data.
+