xml.etree.ElementTree — A API XML ElementTree

Código-fonte: Lib/xml/etree/ElementTree.py

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O módulo xml.etree.ElementTree implementa uma API simples e eficiente para análise e criação de dados XML.

Alterado na versão 3.3: Este módulo usará uma implementação rápida sempre que disponível.

Obsoleto desde a versão 3.3: O módulo xml.etree.cElementTree foi descontinuado.

Aviso

O módulo xml.etree.cElementTree não é seguro contra dados maliciosamente construídos. Se você precisa analisar dados não-confiáveis ou não-autenticados seja Vulnerabilidades em XML.

Tutorial

Esse é um tutorial curto para usar xml.etree.ElementTree (ET na versão resumida). O objetivo é demonstrar alguns conceitos básicos e trechos de códigos do módulo.

Árvore e elementos XML

XML é um formato de dados estritamente hierárquico, e a maneira mais natural de representá-lo é como uma árvore. ET possui duas classes para esse propósito - ElementTree representa todo o documento XML como uma árvore e Element representa um único nó desta árvore. Interações com o documento inteiro (ler e escrever de/para arquivos) são frequentemente feitos em nível de ElementTree. Interações com um único elemento XML e seus subelementos são feitos a nível de Element .

Analisando XML

Usaremos o documento XML fictício country_data.xml como dados de amostra para esta seção:

<?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>

Nós podemos importar esses dados lendo de um arquivo:

import xml.etree.ElementTree as ET
tree = ET.parse('country_data.xml')
root = tree.getroot()

Ou diretamente de uma string:

root = ET.fromstring(country_data_as_string)

fromstring() obtém o XML de uma string e armazena em um Element, que será o elemento raiz dessa árvore. Outras funções de análise sintática podem criar um ElementTree. Cheque a documentação para se certificar sobre qual dado será retornado.

Assim como um Element, root tem uma tag e um dicionário de atributos:

>>> root.tag
'data'
>>> root.attrib
{}

Ele também tem nós filhos sobre os quais nós podemos iterar:

>>> for child in root:
...     print(child.tag, child.attrib)
...
country {'name': 'Liechtenstein'}
country {'name': 'Singapore'}
country {'name': 'Panama'}

Nós filhos são os mais próximos, e nós podemos acessar nós específicos por índices:

>>> root[0][1].text
'2008'

Nota

Nem todos os elementos da entrada XML acabarão como elementos da árvore analisada. Atualmente, este módulo ignora quaisquer comentários XML, instruções de processamento e declarações de tipo de documento na entrada. No entanto, árvores construídas usando a API deste módulo, em vez de serem analisadas a partir de texto XML, podem conter comentários e instruções de processamento; eles serão incluídos ao gerar a saída XML. Uma declaração de tipo de documento pode ser acessada passando uma instância personalizada TreeBuilder para o construtor XMLParser.

A API de pull para análise sem bloqueio

A maioria das funções de análise fornecidas por este módulo exigem que todo o documento seja lido de uma só vez antes de retornar qualquer resultado. É possível usar um XMLParser e alimentar dados nele de forma incremental, mas é uma API de push que chama métodos em um destino da função de retorno, o que é de muito baixo nível e inconveniente para a maioria das necessidades. Às vezes, o que o usuário realmente deseja é ser capaz de analisar XML de forma incremental, sem operações bloqueantes, enquanto desfruta da conveniência de objetos Element totalmente construídos.

A ferramenta mais poderosa para fazer isso é XMLPullParser. Ela não requer uma leitura bloqueante para obter os dados XML e, em vez disso, é alimentada com dados de forma incremental com chamadas de XMLPullParser.feed(). Para obter os elementos XML analisados, chame XMLPullParser.read_events(). Aqui está um exemplo:

>>> 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
mytag text= sometext more text

O caso de uso óbvio são aplicações que operam sem bloqueio, onde os dados XML são recebidos de um soquete ou lidos de forma incremental de algum dispositivo de armazenamento. Nesses casos, leituras bloqueantes são inaceitáveis.

Por ser tão flexível, XMLPullParser pode ser inconveniente de usar em casos de uso mais simples. Se você não se importa que sua aplicação bloqueie a leitura de dados XML, mas ainda assim gostaria de ter recursos de análise incremental, dê uma olhada em iterparse(). Pode ser útil quando você está lendo um documento XML grande e não deseja mantê-lo totalmente na memória.

Onde o feedback imediato através de eventos é desejado, chamar o método XMLPullParser.flush() pode ajudar a reduzir o atraso; certifique-se de estudar as notas de segurança relacionadas.

Encontrando elementos interessantes

Element possui alguns métodos úteis que ajudam a iterar recursivamente sobre toda a subárvore abaixo dele (seus filhos, seus filhos e assim por diante). Por exemplo, 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() encontra apenas elementos com uma tag que são filhos diretos do elemento atual. Element.find() encontra o primeiro filho com uma tag específica, e Element.text acessa o conteúdo de texto do elemento. Element.get() acessa os atributos do elemento:

>>> for country in root.findall('country'):
...     rank = country.find('rank').text
...     name = country.get('name')
...     print(name, rank)
...
Liechtenstein 1
Singapore 4
Panama 68

Uma especificação mais sofisticada de quais elementos procurar é possível usando XPath.

Modificando um arquivo XML

ElementTree fornece uma maneira simples de construir documentos XML e escrevê-los em arquivos. O método ElementTree.write() serve para esse propósito.

Uma vez criado, um objeto Element pode ser manipulado alterando diretamente seus campos (como Element.text), adicionando e modificando atributos (método Element.set()), bem como como adicionar novos filhos (por exemplo, com Element.append()).

Digamos que queremos adicionar um à classificação de cada país e adicionar um atributo updated ao elemento de classificação:

>>> 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')

Nosso XML agora se parece com isto:

<?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>

Podemos remover elementos usando Element.remove(). Digamos que queremos remover todos os países com classificação superior a 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')

Observe que a modificação simultânea durante a iteração pode levar a problemas, assim como ao iterar e modificar listas ou dicionários do Python. Portanto, o exemplo primeiro coleta todos os elementos correspondentes com root.findall(), e só então itera sobre a lista de correspondências.

Nosso XML agora se parece com isto:

<?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>

Construindo documentos XML

A função SubElement() também fornece uma maneira conveniente de criar novos subelementos para um determinado elemento:

>>> 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>

Analisando XML com espaços de nomes

Se a entrada XML tiver espaços de nomes, tags e atributos com prefixos no formato prefixo:algumatag serão expandidos para {uri}algumatag onde prefixo é substituído pelo URI completo. Além disso, se houver um espaço de nomes padrão, esse URI completo será anexado a todas as tags não prefixadas.

Aqui está um exemplo XML que incorpora dois espaços de nomes, um com o prefixo “fictional” e outro servindo como espaço de nomes padrão:

<?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>

Uma maneira de pesquisar e explorar este exemplo XML é adicionar manualmente o URI a cada tag ou atributo no xpath de um find() ou 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 melhor maneira de pesquisar o exemplo XML com espaço de nomes é criar um dicionário com seus próprios prefixos e usá-los nas funções de pesquisa:

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)

Essas duas abordagens resultam no seguinte:

John Cleese
 |--> Lancelot
 |--> Archie Leach
Eric Idle
 |--> Sir Robin
 |--> Gunther
 |--> Commander Clement

Suporte a XPath

Este módulo fornece suporte limitado para expressões XPath para localizar elementos em uma árvore. O objetivo é oferecer suporte a um pequeno subconjunto da sintaxe abreviada; um mecanismo XPath completo está fora do escopo do módulo.

Exemplo

Aqui está um exemplo que demonstra alguns dos recursos XPath do módulo. Estaremos usando o documento XML countrydata da seção Analisando XML:

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]")

Para XML com espaços de nomes, use a notação qualificada usual {espaço-de-nomes}tag:

# All dublin-core "title" tags in the document
root.findall(".//{http://purl.org/dc/elements/1.1/}title")

Supported XPath syntax

Sintaxe	Significado
tag	Selects all child elements with the given tag. For example, spam selects all child elements named spam, and spam/egg selects all grandchildren named egg in all children named spam. {namespace}* selects all tags in the given namespace, {*}spam selects tags named spam in any (or no) namespace, and {}* only selects tags that are not in a namespace. Alterado na versão 3.8: Support for star-wildcards was added.
*	Selects all child elements, including comments and processing instructions. For example, */egg selects all grandchildren named egg.
.	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, .//egg selects all egg elements in the entire tree.
..	Selects the parent element. Returns None if the path attempts to reach the ancestors of the start element (the element find was called on).
[@attrib]	Selects all elements that have the given attribute.
[@attrib='value']	Selects all elements for which the given attribute has the given value. The value cannot contain quotes.
[@attrib!='value']	Selects all elements for which the given attribute does not have the given value. The value cannot contain quotes. Adicionado na versão 3.10.
[tag]	Selects all elements that have a child named tag. Only immediate children are supported.
[.='text']	Selects all elements whose complete text content, including descendants, equals the given text. Adicionado na versão 3.7.
[.!='text']	Selects all elements whose complete text content, including descendants, does not equal the given text. Adicionado na versão 3.10.
[tag='text']	Selects all elements that have a child named tag whose complete text content, including descendants, equals the given text.
[tag!='text']	Selects all elements that have a child named tag whose complete text content, including descendants, does not equal the given text. Adicionado na versão 3.10.
[position]	Selects all elements that are located at the given position. The position can be either an integer (1 is the first position), the expression last() (for the last position), or a position relative to the last position (e.g. last()-1).

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.

Referência

Funções

xml.etree.ElementTree.canonicalize(xml_data=None, *, out=None, from_file=None, **options)

C14N 2.0 transformation function.

Canonicalization is a way to normalise XML output in a way that allows byte-by-byte comparisons and digital signatures. It reduces 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)

The configuration options are as follows:

• with_comments: set to true to include comments (default: false)

• strip_text: set to true to strip whitespace before and after text content

  (default: false)

• rewrite_prefixes: set to true to replace namespace prefixes by “n{number}”

  (default: false)

• 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.

Adicionado na versão 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. An ElementTree will only contain comment nodes if they have been inserted into to the tree using one of the Element 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 is an element tree or an individual element.

Alterado na versão 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 standard XMLParser parser is used. Returns an Element 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 an Element instance.

Adicionado na versão 3.2.

xml.etree.ElementTree.indent(tree, space='  ', level=0)

Appends whitespace to the subtree to indent the tree visually. This can be used to generate pretty-printed XML output. tree can be an Element or ElementTree. space is the whitespace string that will be inserted for each indentation level, two space characters by default. For indenting partial subtrees inside of an already indented tree, pass the initial indentation level as level.

Adicionado na versão 3.9.

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 standard XMLParser parser is used. parser must be a subclass of XMLParser and can only use the default TreeBuilder as a target. Returns an iterator providing (event, elem) pairs; it has a root attribute that references the root element of the resulting XML tree once source is fully read.

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, see XMLPullParser.

Nota

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.

Obsoleto desde a versão 3.4: The parser argument.

Alterado na versão 3.8: The comment and pi events were added.

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 an ElementTree 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 PI objects for them. An ElementTree will only contain processing instruction nodes if they have been inserted into to the tree using one of the Element 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.

Adicionado na versão 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). Use encoding="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 in ElementTree.write(). Returns an (optionally) encoded string containing the XML data.

Alterado na versão 3.4: Added the short_empty_elements parameter.

Alterado na versão 3.8: Added the xml_declaration and default_namespace parameters.

Alterado na versão 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). Use encoding="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 in ElementTree.write(). Returns a list of (optionally) encoded strings containing the XML data. It does not guarantee any specific sequence, except that b"".join(tostringlist(element)) == tostring(element).

Adicionado na versão 3.2.

Alterado na versão 3.4: Added the short_empty_elements parameter.

Alterado na versão 3.8: Added the xml_declaration and default_namespace parameters.

Alterado na versão 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 an Element 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 an Element instance and a dictionary.

XInclude support

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.

Exemplo

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>

Referência

Funções

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 Element instance. If the parse mode is "text", this is a string. If the loader fails, it can return None or raise an exception.

xml.etree.ElementInclude.include(elem, loader=None, base_url=None, max_depth=6)

This function expands XInclude directives in-place in tree pointed by elem. elem is either the root Element or an ElementTree instance to find such 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 as default_loader(). base_url is base URL of the original file, to resolve relative include file references. max_depth is the maximum number of recursive inclusions. Limited to reduce the risk of malicious content explosion. Pass None to disable the limitation.

Alterado na versão 3.9: Added the base_url and max_depth parameters.

Element Objects

class xml.etree.ElementTree.Element(tag, attrib={}, **extra)

Element class. This class defines the Element interface, and provides a reference implementation of this 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, or None. 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 tail None, and the d element has text None 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.

The following dictionary-like methods work on the element attributes.

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)

Gets the element attribute named key.

Returns the attribute value, or default if the attribute was not found.

items()

Returns the element attributes as a sequence of (name, value) pairs. The attributes are returned in an arbitrary order.

keys()

Returns the elements attribute names as a list. The names are returned in an arbitrary order.

set(key, value)

Set the attribute key on the element to value.

The following methods work on the element’s children (subelements).

append(subelement)

Adds the element subelement to the end of this element’s internal list of subelements. Raises TypeError if subelement is not an Element.

extend(subelements)

Appends subelements from an iterable of elements. Raises TypeError if a subelement is not an Element.

Adicionado na versão 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.

insert(index, subelement)

Inserts subelement at the given position in this element. Raises TypeError if subelement is not an Element.

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.

Adicionado na versão 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.

Adicionado na versão 3.2.

itertext()

Creates a text iterator. The iterator loops over this element and all subelements, in document order, and returns all inner text.

Adicionado na versão 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. In a future release of Python, all elements will test as True regardless of whether subelements exist. Instead, prefer explicit len(elem) or elem is not None tests.:

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")

Alterado na versão 3.12: Testing the truth value of an Element emits DeprecationWarning.

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)

ElementTree Objects

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)

Same as Element.find(), starting at the root of the tree.

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.

getroot()

Returns the root element for this tree.

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.

Adicionado na versão 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 is None). 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. If True (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.

Alterado na versão 3.4: Added the short_empty_elements parameter.

Alterado na versão 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")

QName Objects

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.

TreeBuilder Objects

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() and ProcessingInstruction() 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)

Adds text to the current element. data is a string. This should be either a bytestring, or a Unicode string.

end(tag)

Closes the current element. tag is the element name. Returns the closed element.

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.

Adicionado na versão 3.8.

pi(target, text)

Creates a process instruction with the given target name and text. If insert_pis is true, this will also add it to the tree.

Adicionado na versão 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.

Adicionado na versão 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.

Adicionado na versão 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.

Adicionado na versão 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.

Adicionado na versão 3.8.

Objetos 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 the feed() method, and parsing events are translated to a push API - by invoking callbacks on the target object. If target is omitted, the standard TreeBuilder is used. If encoding [1] is given, the value overrides the encoding specified in the XML file.

Alterado na versão 3.8: Parameters are now keyword-only. The html argument is 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 see xml.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 of flush() using hasattr() if used in code running across a variety of Python versions.

Adicionado na versão 3.12.3.

XMLParser.feed() calls target's start(tag, attrs_dict) method for each opening tag, its end(tag) method for each closing tag, and data is processed by method data(data). For further supported callback methods, see the TreeBuilder class. XMLParser.close() calls target's method close(). 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

XMLPullParser Objects

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 see xml.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 of flush() using hasattr() if used in code running across a variety of Python versions.

Adicionado na versão 3.12.3.

close()

Signal the parser that the data stream is terminated. Unlike XMLParser.close(), this method always returns None. Any events not yet retrieved when the parser is closed can still be read with read_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 encountered Element object, or other context value as follows.

• start, end: the current Element.

• comment, pi: the current comment / processing instruction

• start-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 from read_events() will have unpredictable results.

Nota

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.

Adicionado na versão 3.4.

Alterado na versão 3.8: The comment and pi events were added.

Exceções

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

A tuple of line, column numbers, specifying where the error occurred.

Notas de rodapé

[1] (1,2,3,4)

The encoding string included in XML output should conform to the appropriate standards. For example, “UTF-8” is valid, but “UTF8” is not. See https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-EncodingDecl and https://www.iana.org/assignments/character-sets/character-sets.xhtml.