| |
| :mod:`xml.etree.ElementTree` --- The ElementTree XML API |
| ======================================================== |
| |
| .. module:: xml.etree.ElementTree |
| :synopsis: Implementation of the ElementTree API. |
| .. moduleauthor:: Fredrik Lundh <fredrik@pythonware.com> |
| |
| |
| 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 ASCII-only :class:`bytes` object or a :class:`str` object. *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 an |
| ASCII-only :class:`bytes` object or a :class:`str` object. *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 an ASCII-only |
| :class:`bytes` object or a :class:`str` object. *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:`__bool__` 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:: |
| |
| <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 b7d3f1ec> |
| >>> p = tree.find("body/p") # Finds first occurrence of tag p in body |
| >>> p |
| <Element p at 8416e0c> |
| >>> links = p.getiterator("a") # Returns list of all links |
| >>> links |
| [<Element a at b7d4f9ec>, <Element a at b7d4fb0c>] |
| >>> 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 ASCII-only :class:`bytes` object or a :class:`str` object. |
| |
| |
| .. 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 = """ |
| ... <a> |
| ... <b> |
| ... </b> |
| ... <b> |
| ... <c> |
| ... <d> |
| ... </d> |
| ... </c> |
| ... </b> |
| ... </a>""" |
| >>> 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 . |
| |