diff options
| -rw-r--r-- | Doc/library/xml.etree.elementtree.rst | 42 |
1 files changed, 40 insertions, 2 deletions
diff --git a/Doc/library/xml.etree.elementtree.rst b/Doc/library/xml.etree.elementtree.rst index c466731..9f46755 100644 --- a/Doc/library/xml.etree.elementtree.rst +++ b/Doc/library/xml.etree.elementtree.rst @@ -659,7 +659,7 @@ Functions .. function:: tostring(element, encoding="us-ascii", method="xml", *, \ - xml_declaration=None, default_namespace=None, + xml_declaration=None, default_namespace=None, \ short_empty_elements=True) Generates a string representation of an XML element, including all @@ -677,9 +677,13 @@ Functions .. versionadded:: 3.8 The *xml_declaration* and *default_namespace* parameters. + .. versionchanged:: 3.8 + The :func:`tostring` function now preserves the attribute order + specified by the user. + .. function:: tostringlist(element, encoding="us-ascii", method="xml", *, \ - xml_declaration=None, default_namespace=None, + xml_declaration=None, default_namespace=None, \ short_empty_elements=True) Generates a string representation of an XML element, including all @@ -700,6 +704,10 @@ Functions .. versionadded:: 3.8 The *xml_declaration* and *default_namespace* parameters. + .. versionchanged:: 3.8 + The :func:`tostringlist` function now preserves the attribute order + specified by the user. + .. function:: XML(text, parser=None) @@ -930,6 +938,36 @@ Element Objects if element is None: print("element not found") + Prior to Python 3.8, the serialisation order of the XML attributes of + elements was artificially made predictable by sorting the attributes by + their name. Based on the now guaranteed ordering of dicts, this arbitrary + reordering was removed in Python 3.8 to preserve the order in which + attributes were originally parsed or created by user code. + + In general, user code should try not to depend on a specific ordering of + attributes, given that the `XML Information Set + <https://www.w3.org/TR/xml-infoset/>`_ explicitly excludes the attribute + order from conveying information. Code should be prepared to deal with + any ordering on input. In cases where deterministic XML output is required, + e.g. for cryptographic signing or test data sets, canonical serialisation + is available with the :func:`canonicalize` function. + + In cases where canonical output is not applicable but a specific attribute + order is still desirable on output, code should aim for creating the + attributes directly in the desired order, to avoid perceptual mismatches + for readers of the code. In cases where this is difficult to achieve, a + recipe like the following can be applied prior to serialisation to enforce + an order independently from the Element creation:: + + def reorder_attributes(root): + for el in root.iter(): + attrib = el.attrib + if len(attrib) > 1: + # adjust attribute order, e.g. by sorting + attribs = sorted(attrib.items()) + attrib.clear() + attrib.update(attribs) + .. _elementtree-elementtree-objects: |