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Diffstat (limited to 'Doc/library/xml.etree.elementtree.rst')
| -rw-r--r-- | Doc/library/xml.etree.elementtree.rst | 111 |
1 files changed, 100 insertions, 11 deletions
diff --git a/Doc/library/xml.etree.elementtree.rst b/Doc/library/xml.etree.elementtree.rst index 782ebe7..813e0e3 100644 --- a/Doc/library/xml.etree.elementtree.rst +++ b/Doc/library/xml.etree.elementtree.rst @@ -35,10 +35,11 @@ and its sub-elements are done on the :class:`Element` level. Parsing XML ^^^^^^^^^^^ -We'll be using the following XML document contained in a Python string as the -sample data for this section:: +We'll be using the following XML document as the sample data for this section: - countrydata = r'''<?xml version="1.0"?> +.. code-block:: xml + + <?xml version="1.0"?> <data> <country name="Liechtenshtein"> <rank>1</rank> @@ -61,18 +62,20 @@ sample data for this section:: <neighbor name="Colombia" direction="E"/> </country> </data> - ''' -First, import the module and parse the data:: +We can import this data by reading from a file:: import xml.etree.ElementTree as ET + tree = ET.parse('country_data.xml') + root = tree.getroot() - root = ET.fromstring(countrydata) +Or directly from a string:: + + root = ET.fromstring(country_data_as_string) :func:`fromstring` parses XML from a string directly into an :class:`Element`, which is the root element of the parsed tree. Other parsing functions may -create an :class:`ElementTree`. Make sure to check the documentation to be -sure. +create an :class:`ElementTree`. Check the documentation to be sure. As an :class:`Element`, ``root`` has a tag and a dictionary of attributes:: @@ -111,13 +114,27 @@ the sub-tree below it (its children, their children, and so on). For example, {'name': 'Costa Rica', 'direction': 'W'} {'name': 'Colombia', 'direction': 'E'} +:meth:`Element.findall` finds only elements with a tag which are direct +children of the current element. :meth:`Element.find` finds the *first* child +with a particular tag, and :meth:`Element.text` accesses the element's text +content. :meth:`Element.get` accesses the element's attributes:: + + >>> for country in root.findall('country'): + ... rank = country.find('rank').text + ... name = country.get('name') + ... print(name, rank) + ... + Liechtenshtein 1 + Singapore 4 + Panama 68 + More sophisticated specification of which elements to look for is possible by using :ref:`XPath <elementtree-xpath>`. -Building XML documents -^^^^^^^^^^^^^^^^^^^^^^ +Modifying an XML File +^^^^^^^^^^^^^^^^^^^^^ -``ET`` provides a simple way to build XML documents and write them to files. +:class:`ElementTree` provides a simple way to build XML documents and write them to files. The :meth:`ElementTree.write` method serves this purpose. Once created, an :class:`Element` object may be manipulated by directly changing @@ -125,6 +142,78 @@ its fields (such as :attr:`Element.text`), adding and modifying attributes (:meth:`Element.set` method), as well as adding new children (for example with :meth:`Element.append`). +Let's say we want to add one to each country's rank, and add an ``updated`` +attribute to the rank element:: + + >>> for rank in root.iter('rank'): + ... new_rank = int(rank.text) + 1 + ... rank.text = str(new_rank) + ... rank.set('updated', 'yes') + ... + ... tree.write('output.xml') + +Our XML now looks like this: + +.. code-block:: xml + + <?xml version="1.0"?> + <data> + <country name="Liechtenshtein"> + <rank updated="yes">2</rank> + <year>2008</year> + <gdppc>141100</gdppc> + <neighbor name="Austria" direction="E"/> + <neighbor name="Switzerland" direction="W"/> + </country> + <country name="Singapore"> + <rank updated="yes">5</rank> + <year>2011</year> + <gdppc>59900</gdppc> + <neighbor name="Malaysia" direction="N"/> + </country> + <country name="Panama"> + <rank updated="yes">69</rank> + <year>2011</year> + <gdppc>13600</gdppc> + <neighbor name="Costa Rica" direction="W"/> + <neighbor name="Colombia" direction="E"/> + </country> + </data> + +We can remove elements using :meth:`Element.remove`. Let's say we want to +remove all countries with a rank higher than 50:: + + >>> for country in root.findall('country'): + ... rank = int(country.find('rank').text) + ... if rank > 50: + ... root.remove(country) + ... + ... tree.write('output.xml') + +Our XML now looks like this: + +.. code-block:: xml + + <?xml version="1.0"?> + <data> + <country name="Liechtenshtein"> + <rank updated="yes">2</rank> + <year>2008</year> + <gdppc>141100</gdppc> + <neighbor name="Austria" direction="E"/> + <neighbor name="Switzerland" direction="W"/> + </country> + <country name="Singapore"> + <rank updated="yes">5</rank> + <year>2011</year> + <gdppc>59900</gdppc> + <neighbor name="Malaysia" direction="N"/> + </country> + </data> + +Building XML documents +^^^^^^^^^^^^^^^^^^^^^^ + The :func:`SubElement` function also provides a convenient way to create new sub-elements for a given element:: |