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author | Georg Brandl <georg@python.org> | 2007-08-15 14:28:01 (GMT) |
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committer | Georg Brandl <georg@python.org> | 2007-08-15 14:28:01 (GMT) |
commit | 8ec7f656134b1230ab23003a94ba3266d7064122 (patch) | |
tree | bc730d5fb3302dc375edd26b26f750d609b61d72 /Doc/library/xml.etree.elementtree.rst | |
parent | f56181ff53ba00b7bed3997a4dccd9a1b6217b57 (diff) | |
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Move the 2.6 reST doc tree in place.
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diff --git a/Doc/library/xml.etree.elementtree.rst b/Doc/library/xml.etree.elementtree.rst new file mode 100644 index 0000000..ead8d29 --- /dev/null +++ b/Doc/library/xml.etree.elementtree.rst @@ -0,0 +1,444 @@ + +: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. + |