xml.etree.ElementTree
— L'API ElementTree XML¶
Code Source: Lib/xml/etree/ElementTree.py
Le module xml.etree.ElementTree
implémente une API simple et efficace pour analyser et créer des données XML.
Modifié dans la version 3.3: This module will use a fast implementation whenever available.
The xml.etree.cElementTree
module is deprecated.
Avertissement
The xml.etree.ElementTree
module is not secure against
maliciously constructed data. If you need to parse untrusted or
unauthenticated data see Vulnérabilités XML.
Tutoriel¶
Ceci est un petit tutoriel pour utiliser xml.etree.ElementTree
(ET
). Le but est de démontrer quelques composants et les concepts basiques du module.
Arborescence et éléments XML¶
XML est un format de données fondamentalement hiérarchique et la façon la plus naturelle de la représenter est avec un arbre. ET
a deux classes pour ce but- ElementTree
représente l'ensemble du document XML comme un arbre et Element
est représenté en tant que nœud dans cet arbre. Les interactions (lire et écrire vers/depuis des fichiers) sur le document sont habituellement effectués au niveau de ElementTree
. Les interactions sur un seul élément XML et ses sous-éléments sont effectués au niveau de Element
.
Analyse XML¶
Nous utilisons le document XML suivant comme exemple pour cette section :
<?xml version="1.0"?>
<data>
<country name="Liechtenstein">
<rank>1</rank>
<year>2008</year>
<gdppc>141100</gdppc>
<neighbor name="Austria" direction="E"/>
<neighbor name="Switzerland" direction="W"/>
</country>
<country name="Singapore">
<rank>4</rank>
<year>2011</year>
<gdppc>59900</gdppc>
<neighbor name="Malaysia" direction="N"/>
</country>
<country name="Panama">
<rank>68</rank>
<year>2011</year>
<gdppc>13600</gdppc>
<neighbor name="Costa Rica" direction="W"/>
<neighbor name="Colombia" direction="E"/>
</country>
</data>
Nous pouvons importer cette donnée en lisant un fichier :
import xml.etree.ElementTree as ET
tree = ET.parse('country_data.xml')
root = tree.getroot()
Ou depuis une chaîne de caractères :
root = ET.fromstring(country_data_as_string)
fromstring()
analyse le XML depuis une chaîne de caractères vers un Element
, ce dernier est l'élément racine de l'arbre analysé. D'Autres fonctions d'analyse peuvent créer un ElementTree
. Vérifier la documentation pour être sûr.
Comme Element
, root
a une balise et un dictionnaire d'attributs :
>>> root.tag
'data'
>>> root.attrib
{}
Il contient aussi des nœuds enfants que nous pouvons itérer :
>>> for child in root:
... print(child.tag, child.attrib)
...
country {'name': 'Liechtenstein'}
country {'name': 'Singapore'}
country {'name': 'Panama'}
Les enfants sont imbriqués et nous pouvons accéder aux nœuds enfants spécifiques via un index :
>>> root[0][1].text
'2008'
Note
Les éléments du XML d'entrée ne sont pas tous considérés comme des éléments de l'arborescence. Souvent, le module ignore les commentaires XML, les instructions de traitements et la déclaration du type de document dans l'entrée. Néanmoins, les arborescences sont construites en utilisant l'API du module plutôt que d'analyser depuis un texte XML qui peut contenir des commentaires et des instructions de traitements ; ils peuvent être inclus lors de la génération du XML de sortie. Le type de déclaration du document est accessible en passant par une instance de TreeBuilder
dans le constructeur de XMLParser
.
API à flux tiré¶
Most parsing functions provided by this module require the whole document
to be read at once before returning any result. It is possible to use an
XMLParser
and feed data into it incrementally, but it is a push API that
calls methods on a callback target, which is too low-level and inconvenient for
most needs. Sometimes what the user really wants is to be able to parse XML
incrementally, without blocking operations, while enjoying the convenience of
fully constructed Element
objects.
The most powerful tool for doing this is XMLPullParser
. It does not
require a blocking read to obtain the XML data, and is instead fed with data
incrementally with XMLPullParser.feed()
calls. To get the parsed XML
elements, call XMLPullParser.read_events()
. Here is an example:
>>> parser = ET.XMLPullParser(['start', 'end'])
>>> parser.feed('<mytag>sometext')
>>> list(parser.read_events())
[('start', <Element 'mytag' at 0x7fa66db2be58>)]
>>> parser.feed(' more text</mytag>')
>>> for event, elem in parser.read_events():
... print(event)
... print(elem.tag, 'text=', elem.text)
...
end
The obvious use case is applications that operate in a non-blocking fashion where the XML data is being received from a socket or read incrementally from some storage device. In such cases, blocking reads are unacceptable.
Because it's so flexible, XMLPullParser
can be inconvenient to use for
simpler use-cases. If you don't mind your application blocking on reading XML
data but would still like to have incremental parsing capabilities, take a look
at iterparse()
. It can be useful when you're reading a large XML document
and don't want to hold it wholly in memory.
Where immediate feedback through events is wanted, calling method
XMLPullParser.flush()
can help reduce delay;
please make sure to study the related security notes.
Trouver les éléments d'intérêt¶
Element
a quelques méthodes très utiles qui aident à parcourir récursivement tous les sous-arbres (ses enfants, leurs enfants et ainsi de suite). Par exemple, Element.iter()
:
>>> for neighbor in root.iter('neighbor'):
... print(neighbor.attrib)
...
{'name': 'Austria', 'direction': 'E'}
{'name': 'Switzerland', 'direction': 'W'}
{'name': 'Malaysia', 'direction': 'N'}
{'name': 'Costa Rica', 'direction': 'W'}
{'name': 'Colombia', 'direction': 'E'}
Element.findall()
récupère seulement les éléments avec une balise qui sont les descendants directs de l'élément courant. Element.find()
récupère le premier élément avec une balise particulière et Element.text
accède au contenu textuel de l'élément. Element.get()
accède aux attributs de l'élément :
>>> for country in root.findall('country'):
... rank = country.find('rank').text
... name = country.get('name')
... print(name, rank)
...
Liechtenstein 1
Singapore 4
Panama 68
More sophisticated specification of which elements to look for is possible by using XPath.
Modification d'un fichier XML¶
ElementTree
provides a simple way to build XML documents and write them to files.
The ElementTree.write()
method serves this purpose.
Once created, an Element
object may be manipulated by directly changing
its fields (such as Element.text
), adding and modifying attributes
(Element.set()
method), as well as adding new children (for example
with 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')
Maintenant, notre XML ressemble à ceci :
<?xml version="1.0"?>
<data>
<country name="Liechtenstein">
<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 Element.remove()
. Let's say we want to
remove all countries with a rank higher than 50:
>>> for country in root.findall('country'):
... # using root.findall() to avoid removal during traversal
... rank = int(country.find('rank').text)
... if rank > 50:
... root.remove(country)
...
>>> tree.write('output.xml')
Note that concurrent modification while iterating can lead to problems,
just like when iterating and modifying Python lists or dicts.
Therefore, the example first collects all matching elements with
root.findall()
, and only then iterates over the list of matches.
Maintenant, notre XML ressemble à ceci :
<?xml version="1.0"?>
<data>
<country name="Liechtenstein">
<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>
Création de documents XML¶
The SubElement()
function also provides a convenient way to create new
sub-elements for a given element:
>>> a = ET.Element('a')
>>> b = ET.SubElement(a, 'b')
>>> c = ET.SubElement(a, 'c')
>>> d = ET.SubElement(c, 'd')
>>> ET.dump(a)
<a><b /><c><d /></c></a>
Analyse d'un XML avec des espaces de noms¶
If the XML input has namespaces, tags and attributes
with prefixes in the form prefix:sometag
get expanded to
{uri}sometag
where the prefix is replaced by the full URI.
Also, if there is a default namespace,
that full URI gets prepended to all of the non-prefixed tags.
Here is an XML example that incorporates two namespaces, one with the prefix "fictional" and the other serving as the default namespace:
<?xml version="1.0"?>
<actors xmlns:fictional="http://characters.example.com"
xmlns="http://people.example.com">
<actor>
<name>John Cleese</name>
<fictional:character>Lancelot</fictional:character>
<fictional:character>Archie Leach</fictional:character>
</actor>
<actor>
<name>Eric Idle</name>
<fictional:character>Sir Robin</fictional:character>
<fictional:character>Gunther</fictional:character>
<fictional:character>Commander Clement</fictional:character>
</actor>
</actors>
One way to search and explore this XML example is to manually add the
URI to every tag or attribute in the xpath of a
find()
or findall()
:
root = fromstring(xml_text)
for actor in root.findall('{http://people.example.com}actor'):
name = actor.find('{http://people.example.com}name')
print(name.text)
for char in actor.findall('{http://characters.example.com}character'):
print(' |-->', char.text)
A better way to search the namespaced XML example is to create a dictionary with your own prefixes and use those in the search functions:
ns = {'real_person': 'http://people.example.com',
'role': 'http://characters.example.com'}
for actor in root.findall('real_person:actor', ns):
name = actor.find('real_person:name', ns)
print(name.text)
for char in actor.findall('role:character', ns):
print(' |-->', char.text)
Ces deux approches donnent le même résultat :
John Cleese
|--> Lancelot
|--> Archie Leach
Eric Idle
|--> Sir Robin
|--> Gunther
|--> Commander Clement
Additional resources¶
See http://effbot.org/zone/element-index.htm for tutorials and links to other docs.
Prise en charge de XPath¶
This module provides limited support for XPath expressions for locating elements in a tree. The goal is to support a small subset of the abbreviated syntax; a full XPath engine is outside the scope of the module.
Exemple¶
Here's an example that demonstrates some of the XPath capabilities of the
module. We'll be using the countrydata
XML document from the
Parsing XML section:
import xml.etree.ElementTree as ET
root = ET.fromstring(countrydata)
# Top-level elements
root.findall(".")
# All 'neighbor' grand-children of 'country' children of the top-level
# elements
root.findall("./country/neighbor")
# Nodes with name='Singapore' that have a 'year' child
root.findall(".//year/..[@name='Singapore']")
# 'year' nodes that are children of nodes with name='Singapore'
root.findall(".//*[@name='Singapore']/year")
# All 'neighbor' nodes that are the second child of their parent
root.findall(".//neighbor[2]")
For XML with namespaces, use the usual qualified {namespace}tag
notation:
# All dublin-core "title" tags in the document
root.findall(".//{http://purl.org/dc/elements/1.1/}title")
Prise en charge de la syntaxe XPath¶
Syntaxe |
Signification |
---|---|
|
Sélectionne tous les éléments enfants avec une balise donnée. Par exemple, Modifié dans la version 3.8: Support for star-wildcards was added. |
|
Selects all child elements, including comments and
processing instructions. For example, |
|
Selects the current node. This is mostly useful at the beginning of the path, to indicate that it's a relative path. |
|
Selects all subelements, on all levels beneath the
current element. For example, |
|
Selects the parent element. Returns |
|
Selects all elements that have the given attribute. |
|
Selects all elements for which the given attribute has the given value. The value cannot contain quotes. |
|
Selects all elements that have a child named
|
|
Selects all elements whose complete text content,
including descendants, equals the given Nouveau dans la version 3.7. |
|
Selects all elements that have a child named
|
|
Selects all elements that are located at the given
position. The position can be either an integer
(1 is the first position), the expression |
Predicates (expressions within square brackets) must be preceded by a tag
name, an asterisk, or another predicate. position
predicates must be
preceded by a tag name.
Référence¶
Fonctions¶
-
xml.etree.ElementTree.
canonicalize
(xml_data=None, *, out=None, from_file=None, **options)¶ C14N 2.0 fonction de transformation.
Canonicalization is a way to normalise XML output in a way that allows byte-by-byte comparisons and digital signatures. It reduced the freedom that XML serializers have and instead generates a more constrained XML representation. The main restrictions regard the placement of namespace declarations, the ordering of attributes, and ignorable whitespace.
This function takes an XML data string (xml_data) or a file path or file-like object (from_file) as input, converts it to the canonical form, and writes it out using the out file(-like) object, if provided, or returns it as a text string if not. The output file receives text, not bytes. It should therefore be opened in text mode with
utf-8
encoding.Typical uses:
xml_data = "<root>...</root>" print(canonicalize(xml_data)) with open("c14n_output.xml", mode='w', encoding='utf-8') as out_file: canonicalize(xml_data, out=out_file) with open("c14n_output.xml", mode='w', encoding='utf-8') as out_file: canonicalize(from_file="inputfile.xml", out=out_file)
Les options de configuration sont les suivantes :
with_comments : attribue à vrai pour inclure les commentaires (par défaut : faux)
- strip_text: set to true to strip whitespace before and after text content
(par défaut : faux)
- rewrite_prefixes: set to true to replace namespace prefixes by "n{number}"
(par défaut : faux)
- qname_aware_tags: a set of qname aware tag names in which prefixes
should be replaced in text content (default: empty)
- qname_aware_attrs: a set of qname aware attribute names in which prefixes
should be replaced in text content (default: empty)
exclude_attrs: a set of attribute names that should not be serialised
exclude_tags: a set of tag names that should not be serialised
In the option list above, "a set" refers to any collection or iterable of strings, no ordering is expected.
Nouveau dans la version 3.8.
-
xml.etree.ElementTree.
Comment
(text=None)¶ Comment element factory. This factory function creates a special element that will be serialized as an XML comment by the standard serializer. The comment string can be either a bytestring or a Unicode string. text is a string containing the comment string. Returns an element instance representing a comment.
Note that
XMLParser
skips over comments in the input instead of creating comment objects for them. AnElementTree
will only contain comment nodes if they have been inserted into to the tree using one of theElement
methods.
-
xml.etree.ElementTree.
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 est un élément de l'arborescence ou un élément individuel.
Modifié dans la version 3.8: The
dump()
function now preserves the attribute order specified by the user.
-
xml.etree.ElementTree.
fromstring
(text, parser=None)¶ Parses an XML section from a string constant. Same as
XML()
. text is a string containing XML data. parser is an optional parser instance. If not given, the standardXMLParser
parser is used. Returns anElement
instance.
-
xml.etree.ElementTree.
fromstringlist
(sequence, parser=None)¶ Parses an XML document from a sequence of string fragments. sequence is a list or other sequence containing XML data fragments. parser is an optional parser instance. If not given, the standard
XMLParser
parser is used. Returns anElement
instance.Nouveau dans la version 3.2.
-
xml.etree.ElementTree.
iselement
(element)¶ Check if an object appears to be a valid element object. element is an element instance. Return
True
if this is an element object.
-
xml.etree.ElementTree.
iterparse
(source, events=None, parser=None)¶ 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 sequence of events to report back. The supported events are the strings
"start"
,"end"
,"comment"
,"pi"
,"start-ns"
and"end-ns"
(the "ns" events are used to get detailed namespace information). If events is omitted, only"end"
events are reported. parser is an optional parser instance. If not given, the standardXMLParser
parser is used. parser must be a subclass ofXMLParser
and can only use the defaultTreeBuilder
as a target. Returns an iterator providing(event, elem)
pairs.Note that while
iterparse()
builds the tree incrementally, it issues blocking reads on source (or the file it names). As such, it's unsuitable for applications where blocking reads can't be made. For fully non-blocking parsing, seeXMLPullParser
.Note
iterparse()
only guarantees that it has seen the ">" character of a starting tag when it emits a "start" event, so the attributes are defined, but the contents of the text and tail attributes are undefined at that point. The same applies to the element children; they may or may not be present.If you need a fully populated element, look for "end" events instead.
Obsolète depuis la version 3.4: L'argument parser.
Modifié dans la version 3.8: Les évènements
comment
etpi
ont été ajoutés.
-
xml.etree.ElementTree.
parse
(source, parser=None)¶ 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
XMLParser
parser is used. Returns anElementTree
instance.
-
xml.etree.ElementTree.
ProcessingInstruction
(target, text=None)¶ 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.
Note that
XMLParser
skips over processing instructions in the input instead of creating comment objects for them. AnElementTree
will only contain processing instruction nodes if they have been inserted into to the tree using one of theElement
methods.
-
xml.etree.ElementTree.
register_namespace
(prefix, uri)¶ Registers a namespace prefix. The registry is global, and any existing mapping for either the given prefix or the namespace URI will be removed. prefix is a namespace prefix. uri is a namespace uri. Tags and attributes in this namespace will be serialized with the given prefix, if at all possible.
Nouveau dans la version 3.2.
-
xml.etree.ElementTree.
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 bytestrings 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.
-
xml.etree.ElementTree.
tostring
(element, encoding="us-ascii", method="xml", *, xml_declaration=None, default_namespace=None, short_empty_elements=True)¶ Generates a string representation of an XML element, including all subelements. element is an
Element
instance. encoding 1 is the output encoding (default is US-ASCII). Useencoding="unicode"
to generate a Unicode string (otherwise, a bytestring is generated). method is either"xml"
,"html"
or"text"
(default is"xml"
). xml_declaration, default_namespace and short_empty_elements has the same meaning as inElementTree.write()
. Returns an (optionally) encoded string containing the XML data.Nouveau dans la version 3.4: Le paramètre short_empty_elements.
Nouveau dans la version 3.8: Les paramètres xml_declaration et default_namespace.
Modifié dans la version 3.8: The
tostring()
function now preserves the attribute order specified by the user.
-
xml.etree.ElementTree.
tostringlist
(element, encoding="us-ascii", method="xml", *, xml_declaration=None, default_namespace=None, short_empty_elements=True)¶ Generates a string representation of an XML element, including all subelements. element is an
Element
instance. encoding 1 is the output encoding (default is US-ASCII). Useencoding="unicode"
to generate a Unicode string (otherwise, a bytestring is generated). method is either"xml"
,"html"
or"text"
(default is"xml"
). xml_declaration, default_namespace and short_empty_elements has the same meaning as inElementTree.write()
. Returns a list of (optionally) encoded strings containing the XML data. It does not guarantee any specific sequence, except thatb"".join(tostringlist(element)) == tostring(element)
.Nouveau dans la version 3.2.
Nouveau dans la version 3.4: Le paramètre short_empty_elements.
Nouveau dans la version 3.8: Les paramètres xml_declaration et default_namespace.
Modifié dans la version 3.8: The
tostringlist()
function now preserves the attribute order specified by the user.
-
xml.etree.ElementTree.
XML
(text, parser=None)¶ 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. parser is an optional parser instance. If not given, the standard
XMLParser
parser is used. Returns anElement
instance.
-
xml.etree.ElementTree.
XMLID
(text, parser=None)¶ 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. parser is an optional parser instance. If not given, the standard
XMLParser
parser is used. Returns a tuple containing anElement
instance and a dictionary.
Prise en charge de XInclude¶
This module provides limited support for
XInclude directives, via the xml.etree.ElementInclude
helper module. This module can be used to insert subtrees and text strings into element trees, based on information in the tree.
Exemple¶
Here's an example that demonstrates use of the XInclude module. To include an XML document in the current document, use the {http://www.w3.org/2001/XInclude}include
element and set the parse attribute to "xml"
, and use the href attribute to specify the document to include.
<?xml version="1.0"?>
<document xmlns:xi="http://www.w3.org/2001/XInclude">
<xi:include href="source.xml" parse="xml" />
</document>
By default, the href attribute is treated as a file name. You can use custom loaders to override this behaviour. Also note that the standard helper does not support XPointer syntax.
To process this file, load it as usual, and pass the root element to the xml.etree.ElementTree
module:
from xml.etree import ElementTree, ElementInclude
tree = ElementTree.parse("document.xml")
root = tree.getroot()
ElementInclude.include(root)
The ElementInclude module replaces the {http://www.w3.org/2001/XInclude}include
element with the root element from the source.xml document. The result might look something like this:
<document xmlns:xi="http://www.w3.org/2001/XInclude">
<para>This is a paragraph.</para>
</document>
If the parse attribute is omitted, it defaults to "xml". The href attribute is required.
To include a text document, use the {http://www.w3.org/2001/XInclude}include
element, and set the parse attribute to "text":
<?xml version="1.0"?>
<document xmlns:xi="http://www.w3.org/2001/XInclude">
Copyright (c) <xi:include href="year.txt" parse="text" />.
</document>
The result might look something like:
<document xmlns:xi="http://www.w3.org/2001/XInclude">
Copyright (c) 2003.
</document>
Référence¶
Fonctions¶
-
xml.etree.ElementInclude.
default_loader
(href, parse, encoding=None)¶ Default loader. This default loader reads an included resource from disk. href is a URL. parse is for parse mode either "xml" or "text". encoding is an optional text encoding. If not given, encoding is
utf-8
. Returns the expanded resource. If the parse mode is"xml"
, this is an ElementTree instance. If the parse mode is "text", this is a Unicode string. If the loader fails, it can return None or raise an exception.
-
xml.etree.ElementInclude.
include
(elem, loader=None)¶ This function expands XInclude directives. elem is the root element. loader is an optional resource loader. If omitted, it defaults to
default_loader()
. If given, it should be a callable that implements the same interface asdefault_loader()
. Returns the expanded resource. If the parse mode is"xml"
, this is an ElementTree instance. If the parse mode is "text", this is a Unicode string. If the loader fails, it can return None or raise an exception.
Objets Elements¶
-
class
xml.etree.ElementTree.
Element
(tag, attrib={}, **extra)¶ Classe Element. Cette classe définit l'interface Element et fournit une implémentation de référence de cette interface.
The element name, attribute names, and attribute values can be either bytestrings or Unicode strings. tag is the element name. attrib is an optional dictionary, containing element attributes. extra contains additional attributes, given as keyword arguments.
-
tag
¶ A string identifying what kind of data this element represents (the element type, in other words).
-
text
¶ -
tail
¶ These attributes can be used to hold additional data associated with the element. Their values are usually strings but may be any application-specific object. If the element is created from an XML file, the text attribute holds either the text between the element's start tag and its first child or end tag, or
None
, and the tail attribute holds either the text between the element's end tag and the next tag, orNone
. For the XML data<a><b>1<c>2<d/>3</c></b>4</a>
the a element has
None
for both text and tail attributes, the b element has text"1"
and tail"4"
, the c element has text"2"
and tailNone
, and the d element has textNone
and tail"3"
.To collect the inner text of an element, see
itertext()
, for example"".join(element.itertext())
.Applications may store arbitrary objects in these attributes.
-
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.
Les méthodes dictionnaire-compatibles suivantes traitent les attributs de l'élément.
-
clear
()¶ Resets an element. This function removes all subelements, clears all attributes, and sets the text and tail attributes to
None
.
-
get
(key, default=None)¶ Accède à l'attribut de l'élément nommé key.
Renvoie la valeur de l'attribut ou default si l'attribut n'a pas été trouvé.
-
items
()¶ Renvoie les attributs de l'élément comme une séquence de paire (nom, valeur). Les attributs sont renvoyés un l'ordre arbitraire.
-
keys
()¶ Returns the elements attribute names as a list. The names are returned in an arbitrary order.
-
set
(key, value)¶ Change l'attribut key à l'élément value.
Les méthodes suivantes traitent les éléments enfants (sous-éléments).
-
append
(subelement)¶ Adds the element subelement to the end of this element's internal list of subelements. Raises
TypeError
if subelement is not anElement
.
-
extend
(subelements)¶ Appends subelements from a sequence object with zero or more elements. Raises
TypeError
if a subelement is not anElement
.Nouveau dans la version 3.2.
-
find
(match, namespaces=None)¶ Finds the first subelement matching match. match may be a tag name or a path. Returns an element instance or
None
. namespaces is an optional mapping from namespace prefix to full name. Pass''
as prefix to move all unprefixed tag names in the expression into the given namespace.
-
findall
(match, namespaces=None)¶ Finds all matching subelements, by tag name or path. Returns a list containing all matching elements in document order. namespaces is an optional mapping from namespace prefix to full name. Pass
''
as prefix to move all unprefixed tag names in the expression into the given namespace.
-
findtext
(match, default=None, namespaces=None)¶ Finds text for the first subelement matching match. match may be a tag name or a 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. namespaces is an optional mapping from namespace prefix to full name. Pass
''
as prefix to move all unprefixed tag names in the expression into the given namespace.
-
getchildren
()¶ Deprecated since version 3.2, will be removed in version 3.9: Use
list(elem)
or iteration.
-
getiterator
(tag=None)¶ Deprecated since version 3.2, will be removed in version 3.9: Use method
Element.iter()
instead.
-
insert
(index, subelement)¶ Inserts subelement at the given position in this element. Raises
TypeError
if subelement is not anElement
.
-
iter
(tag=None)¶ Creates a tree iterator with the current element as the root. The iterator iterates over this element and all elements below it, in document (depth first) order. If tag is not
None
or'*'
, only elements whose tag equals tag are returned from the iterator. If the tree structure is modified during iteration, the result is undefined.Nouveau dans la version 3.2.
-
iterfind
(match, namespaces=None)¶ Finds all matching subelements, by tag name or path. Returns an iterable yielding all matching elements in document order. namespaces is an optional mapping from namespace prefix to full name.
Nouveau dans la version 3.2.
-
itertext
()¶ Creates a text iterator. The iterator loops over this element and all subelements, in document order, and returns all inner text.
Nouveau dans la version 3.2.
-
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.
-
remove
(subelement)¶ Removes subelement from the element. Unlike the find* 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:__delitem__()
,__getitem__()
,__setitem__()
,__len__()
.Caution: Elements with no subelements will test as
False
. This behavior will change in future versions. Use specificlen(elem)
orelem is None
test instead.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")
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 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
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)
-
Objets ElementTree¶
-
class
xml.etree.ElementTree.
ElementTree
(element=None, file=None)¶ 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.
-
_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.
-
find
(match, namespaces=None)¶ Comme
Element.find()
, commence à la racine de l'arbre.
-
findall
(match, namespaces=None)¶ Same as
Element.findall()
, starting at the root of the tree.
-
findtext
(match, default=None, namespaces=None)¶ Same as
Element.findtext()
, starting at the root of the tree.
-
getiterator
(tag=None)¶ Deprecated since version 3.2, will be removed in version 3.9: Use method
ElementTree.iter()
instead.
-
getroot
()¶ Renvoie l'élément racine de l'arbre.
-
iter
(tag=None)¶ 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).
-
iterfind
(match, namespaces=None)¶ Same as
Element.iterfind()
, starting at the root of the tree.Nouveau dans la version 3.2.
-
parse
(source, parser=None)¶ 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
XMLParser
parser is used. Returns the section root element.
-
write
(file, encoding="us-ascii", xml_declaration=None, default_namespace=None, method="xml", *, short_empty_elements=True)¶ 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). xml_declaration controls if an XML declaration should be added to the file. Use
False
for never,True
for always,None
for only if not US-ASCII or UTF-8 or Unicode (default isNone
). default_namespace sets the default XML namespace (for "xmlns"). method is either"xml"
,"html"
or"text"
(default is"xml"
). The keyword-only short_empty_elements parameter controls the formatting of elements that contain no content. IfTrue
(the default), they are emitted as a single self-closed tag, otherwise they are emitted as a pair of start/end tags.The output is either a string (
str
) or binary (bytes
). This is controlled by the encoding argument. If encoding is"unicode"
, the output is a string; otherwise, it's binary. Note that this may conflict with the type of file if it's an open file object; make sure you do not try to write a string to a binary stream and vice versa.Nouveau dans la version 3.4: Le paramètre short_empty_elements.
Modifié dans la version 3.8: The
write()
method now preserves the attribute order specified by the user.
-
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 0xb77e6fac>
>>> p = tree.find("body/p") # Finds first occurrence of tag p in body
>>> p
<Element 'p' at 0xb77ec26c>
>>> links = list(p.iter("a")) # Returns list of all links
>>> links
[<Element 'a' at 0xb77ec2ac>, <Element 'a' at 0xb77ec1cc>]
>>> for i in links: # Iterates through all found links
... i.attrib["target"] = "blank"
>>> tree.write("output.xhtml")
Objets QName¶
-
class
xml.etree.ElementTree.
QName
(text_or_uri, tag=None)¶ 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 a URI, and this argument is interpreted as a local name.
QName
instances are opaque.
Objets TreeBuilder¶
-
class
xml.etree.ElementTree.
TreeBuilder
(element_factory=None, *, comment_factory=None, pi_factory=None, insert_comments=False, insert_pis=False)¶ Generic element structure builder. This builder converts a sequence of start, data, end, comment and pi 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.
element_factory, when given, must be a callable accepting two positional arguments: a tag and a dict of attributes. It is expected to return a new element instance.
The comment_factory and pi_factory functions, when given, should behave like the
Comment()
andProcessingInstruction()
functions to create comments and processing instructions. When not given, the default factories will be used. When insert_comments and/or insert_pis is true, comments/pis will be inserted into the tree if they appear within the root element (but not outside of it).-
close
()¶ Flushes the builder buffers, and returns the toplevel document element. Returns an
Element
instance.
-
data
(data)¶ Ajoute du texte à l'élément courant. data est une chaîne de caractères. Cela peut être une chaîne d'octets ou une chaîne Unicode.
-
end
(tag)¶ Ferme l'élément courant. tag est le nom de l'élément. Renvoie l'élément fermé.
-
start
(tag, attrs)¶ Opens a new element. tag is the element name. attrs is a dictionary containing element attributes. Returns the opened element.
-
comment
(text)¶ Creates a comment with the given text. If
insert_comments
is true, this will also add it to the tree.Nouveau dans la version 3.8.
-
pi
(target, text)¶ Creates a comment with the given target name and text. If
insert_pis
is true, this will also add it to the tree.Nouveau dans la version 3.8.
In addition, a custom
TreeBuilder
object can provide the following methods:-
doctype
(name, pubid, system)¶ Handles a doctype declaration. name is the doctype name. pubid is the public identifier. system is the system identifier. This method does not exist on the default
TreeBuilder
class.Nouveau dans la version 3.2.
-
start_ns
(prefix, uri)¶ Is called whenever the parser encounters a new namespace declaration, before the
start()
callback for the opening element that defines it. prefix is''
for the default namespace and the declared namespace prefix name otherwise. uri is the namespace URI.Nouveau dans la version 3.8.
-
end_ns
(prefix)¶ Is called after the
end()
callback of an element that declared a namespace prefix mapping, with the name of the prefix that went out of scope.Nouveau dans la version 3.8.
-
-
class
xml.etree.ElementTree.
C14NWriterTarget
(write, *, with_comments=False, strip_text=False, rewrite_prefixes=False, qname_aware_tags=None, qname_aware_attrs=None, exclude_attrs=None, exclude_tags=None)¶ A C14N 2.0 writer. Arguments are the same as for the
canonicalize()
function. This class does not build a tree but translates the callback events directly into a serialised form using the write function.Nouveau dans la version 3.8.
Objets XMLParser¶
-
class
xml.etree.ElementTree.
XMLParser
(*, target=None, encoding=None)¶ This class is the low-level building block of the module. It uses
xml.parsers.expat
for efficient, event-based parsing of XML. It can be fed XML data incrementally with thefeed()
method, and parsing events are translated to a push API - by invoking callbacks on the target object. If target is omitted, the standardTreeBuilder
is used. If encoding 1 is given, the value overrides the encoding specified in the XML file.Modifié dans la version 3.8: Parameters are now keyword-only. The html argument no longer supported.
-
close
()¶ Finishes feeding data to the parser. Returns the result of calling the
close()
method of the target passed during construction; by default, this is the toplevel document element.
-
feed
(data)¶ Feeds data to the parser. data is encoded data.
-
flush
()¶ Triggers parsing of any previously fed unparsed data, which can be used to ensure more immediate feedback, in particular with Expat >=2.6.0. The implementation of
flush()
temporarily disables reparse deferral with Expat (if currently enabled) and triggers a reparse. Disabling reparse deferral has security consequences; please seexml.parsers.expat.xmlparser.SetReparseDeferralEnabled()
for details.Note that
flush()
has been backported to some prior releases of CPython as a security fix. Check for availability offlush()
usinghasattr()
if used in code running across a variety of Python versions.Nouveau dans la version 3.8.19.
XMLParser.feed()
calls target'sstart(tag, attrs_dict)
method for each opening tag, itsend(tag)
method for each closing tag, and data is processed by methoddata(data)
. For further supported callback methods, see theTreeBuilder
class.XMLParser.close()
calls target's methodclose()
.XMLParser
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 XMLParser >>> 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 = XMLParser(target=target) >>> exampleXml = """ ... <a> ... <b> ... </b> ... <b> ... <c> ... <d> ... </d> ... </c> ... </b> ... </a>""" >>> parser.feed(exampleXml) >>> parser.close() 4
-
Objets XMLPullParser¶
-
class
xml.etree.ElementTree.
XMLPullParser
(events=None)¶ A pull parser suitable for non-blocking applications. Its input-side API is similar to that of
XMLParser
, but instead of pushing calls to a callback target,XMLPullParser
collects an internal list of parsing events and lets the user read from it. events is a sequence of events to report back. The supported events are the strings"start"
,"end"
,"comment"
,"pi"
,"start-ns"
and"end-ns"
(the "ns" events are used to get detailed namespace information). If events is omitted, only"end"
events are reported.-
feed
(data)¶ Feed the given bytes data to the parser.
-
flush
()¶ Triggers parsing of any previously fed unparsed data, which can be used to ensure more immediate feedback, in particular with Expat >=2.6.0. The implementation of
flush()
temporarily disables reparse deferral with Expat (if currently enabled) and triggers a reparse. Disabling reparse deferral has security consequences; please seexml.parsers.expat.xmlparser.SetReparseDeferralEnabled()
for details.Note that
flush()
has been backported to some prior releases of CPython as a security fix. Check for availability offlush()
usinghasattr()
if used in code running across a variety of Python versions.Nouveau dans la version 3.8.19.
-
close
()¶ Signal the parser that the data stream is terminated. Unlike
XMLParser.close()
, this method always returnsNone
. Any events not yet retrieved when the parser is closed can still be read withread_events()
.
-
read_events
()¶ Return an iterator over the events which have been encountered in the data fed to the parser. The iterator yields
(event, elem)
pairs, where event is a string representing the type of event (e.g."end"
) and elem is the encounteredElement
object, or other context value as follows.start
,end
: the current Element.comment
,pi
: the current comment / processing instructionstart-ns
: a tuple(prefix, uri)
naming the declared namespace mapping.end-ns
:None
(this may change in a future version)
Events provided in a previous call to
read_events()
will not be yielded again. Events are consumed from the internal queue only when they are retrieved from the iterator, so multiple readers iterating in parallel over iterators obtained fromread_events()
will have unpredictable results.
Note
XMLPullParser
only guarantees that it has seen the ">" character of a starting tag when it emits a "start" event, so the attributes are defined, but the contents of the text and tail attributes are undefined at that point. The same applies to the element children; they may or may not be present.If you need a fully populated element, look for "end" events instead.
Nouveau dans la version 3.4.
Modifié dans la version 3.8: Les évènements
comment
etpi
ont été ajoutés.-
Exceptions¶
-
class
xml.etree.ElementTree.
ParseError
¶ XML parse error, raised by the various parsing methods in this module when parsing fails. The string representation of an instance of this exception will contain a user-friendly error message. In addition, it will have the following attributes available:
-
code
¶ A numeric error code from the expat parser. See the documentation of
xml.parsers.expat
for the list of error codes and their meanings.
-
position
¶ Un n-uplet de numéro de ligne, de colonne indiquant le lieu d'apparition de l'erreur.
-
Notes
- 1(1,2,3,4)
La chaîne de caractères encodée inclue dans la sortie XML doit être conforme aux standards. Par exemple, « UTF-8 » est valide, mais pas « UTF8 ». Voir https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-EncodingDecl et https://www.iana.org/assignments/character-sets/character-sets.xhtml.