diff -r ffa851df0825 -r 2fb8b9db1c86 symbian-qemu-0.9.1-12/python-2.6.1/Doc/library/xml.etree.elementtree.rst --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/symbian-qemu-0.9.1-12/python-2.6.1/Doc/library/xml.etree.elementtree.rst Fri Jul 31 15:01:17 2009 +0100 @@ -0,0 +1,523 @@ + +:mod:`xml.etree.ElementTree` --- The ElementTree XML API +======================================================== + +.. module:: xml.etree.ElementTree + :synopsis: Implementation of the ElementTree API. +.. moduleauthor:: Fredrik Lundh + + +.. 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`. + +See http://effbot.org/zone/element-index.htm for tutorials and links to other +docs. Fredrik Lundh's page is also the location of the development version of the +xml.etree.ElementTree. + +.. _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 :term:`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:: _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(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:: 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 :term:`iterator` containing all matching elements, in document + order. + + + .. method:: 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:: 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:: getroot() + + Returns the root element for this tree. + + + .. method:: 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:: 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* [1]_ is the output encoding + (default is US-ASCII). + +This is the XML file that is going to be manipulated:: + + + + Example page + + +

Moved to example.org + or example.com.

+ + + +Example of changing the attribute "target" of every link in first paragraph:: + + >>> from xml.etree.ElementTree import ElementTree + >>> tree = ElementTree() + >>> tree.parse("index.xhtml") + + >>> p = tree.find("body/p") # Finds first occurrence of tag p in body + >>> p + + >>> links = p.getiterator("a") # Returns list of all links + >>> links + [, ] + >>> 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]) + + 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:: close() + + Flushes the parser buffers, and returns the toplevel document + element. Returns an Element instance. + + + .. method:: 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:: 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. + + +.. _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:: close() + + Finishes feeding data to the parser. Returns an element structure. + + + .. method:: doctype(name, pubid, system) + + Handles a doctype declaration. *name* is the doctype name. *pubid* is the + public identifier. *system* is the system identifier. + + + .. method:: feed(data) + + Feeds data to the parser. *data* is encoded data. + +:meth:`XMLTreeBuilder.feed` calls *target*\'s :meth:`start` method +for each opening tag, its :meth:`end` method for each closing tag, +and data is processed by method :meth:`data`. :meth:`XMLTreeBuilder.close` +calls *target*\'s method :meth:`close`. +:class:`XMLTreeBuilder` 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 XMLTreeBuilder + >>> 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 = XMLTreeBuilder(target=target) + >>> exampleXml = """ + ... + ... + ... + ... + ... + ... + ... + ... + ... + ... """ + >>> parser.feed(exampleXml) + >>> parser.close() + 4 + + +.. 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 . +