QDomDocument

The QDomDocument class represents an XML document. More…

Inheritance diagram of PySide6.QtXml.QDomDocument

Synopsis

Functions

Detailed Description

The QDomDocument class represents the entire XML document. Conceptually, it is the root of the document tree, and provides the primary access to the document’s data.

Since elements, text nodes, comments, processing instructions, etc., cannot exist outside the context of a document, the document class also contains the factory functions needed to create these objects. The node objects created have an ownerDocument() function which associates them with the document within whose context they were created. The DOM classes that will be used most often are QDomNode , QDomDocument , QDomElement and QDomText .

The parsed XML is represented internally by a tree of objects that can be accessed using the various QDom classes. All QDom classes only reference objects in the internal tree. The internal objects in the DOM tree will get deleted once the last QDom object referencing them or the QDomDocument itself is deleted.

Creation of elements, text nodes, etc. is done using the various factory functions provided in this class. Using the default constructors of the QDom classes will only result in empty objects that cannot be manipulated or inserted into the Document.

The QDomDocument class has several functions for creating document data, for example, createElement() , createTextNode() , createComment() , createCDATASection() , createProcessingInstruction() , createAttribute() and createEntityReference() . Some of these functions have versions that support namespaces, i.e. createElementNS() and createAttributeNS() . The createDocumentFragment() function is used to hold parts of the document; this is useful for manipulating for complex documents.

The entire content of the document is set with setContent() . This function parses the string it is passed as an XML document and creates the DOM tree that represents the document. The root element is available using documentElement() . The textual representation of the document can be obtained using toString() .

Note

The DOM tree might end up reserving a lot of memory if the XML document is big. For such documents, the QXmlStreamReader or the QXmlQuery classes might be better solutions.

It is possible to insert a node from another document into the document using importNode() .

You can obtain a list of all the elements that have a particular tag with elementsByTagName() or with elementsByTagNameNS() .

The QDom classes are typically used as follows:

doc = QDomDocument("mydocument")
file = QFile("mydocument.xml")
if not file.open(QIODevice.ReadOnly):
    return
if not doc.setContent(file):
    file.close()
    return

file.close()
# print out the element names of all elements that are direct children
# of the outermost element.
docElem = doc.documentElement()
n = docElem.firstChild()
while not n.isNull():
    e = n.toElement() # try to convert the node to an element.
    if(not e.isNull()) {
        print(qPrintable(e.tagName()), '\n' # the node really is an element.)

    n = n.nextSibling()

# Here we append a new element to the end of the document
elem = doc.createElement("img")
elem.setAttribute("src", "myimage.png")
docElem.appendChild(elem)

Once doc and elem go out of scope, the whole internal tree representing the XML document is deleted.

To create a document using DOM use code like this:

doc = QDomDocument()
root = doc.createElement("MyML")
doc.appendChild(root)
tag = doc.createElement("Greeting")
root.appendChild(tag)
t = doc.createTextNode("Hello World")
tag.appendChild(t)
xml = doc.toString()

For further information about the Document Object Model see the Document Object Model (DOM) Level 1 and Level 2 Core Specifications.

class PySide6.QtXml.QDomDocument

PySide6.QtXml.QDomDocument(x)

PySide6.QtXml.QDomDocument(doctype)

PySide6.QtXml.QDomDocument(name)

Parameters

Constructs an empty document.

Constructs a copy of x.

The data of the copy is shared (shallow copy): modifying one node will also change the other. If you want to make a deep copy, use cloneNode() .

Creates a document with the document type doctype.

Creates a document and sets the name of the document type to name.

PySide6.QtXml.QDomDocument.createAttribute(name)
Parameters

name – str

Return type

PySide6.QtXml.QDomAttr

Creates a new attribute called name that can be inserted into an element, e.g. using setAttributeNode() .

If name is not a valid XML name, the behavior of this function is governed by InvalidDataPolicy .

PySide6.QtXml.QDomDocument.createAttributeNS(nsURI, qName)
Parameters

  • nsURI – str

  • qName – str

Return type

PySide6.QtXml.QDomAttr

Creates a new attribute with namespace support that can be inserted into an element. The name of the attribute is qName and the namespace URI is nsURI. This function also sets prefix() and localName() to appropriate values (depending on qName).

If qName is not a valid XML name, the behavior of this function is governed by InvalidDataPolicy .

PySide6.QtXml.QDomDocument.createCDATASection(data)
Parameters

data – str

Return type

PySide6.QtXml.QDomCDATASection

Creates a new CDATA section for the string value that can be inserted into the document, e.g. using appendChild() .

If value contains characters which cannot be stored in a CDATA section, the behavior of this function is governed by InvalidDataPolicy .

PySide6.QtXml.QDomDocument.createComment(data)
Parameters

data – str

Return type

PySide6.QtXml.QDomComment

Creates a new comment for the string value that can be inserted into the document, e.g. using appendChild() .

If value contains characters which cannot be stored in an XML comment, the behavior of this function is governed by InvalidDataPolicy .

PySide6.QtXml.QDomDocument.createDocumentFragment()
Return type

PySide6.QtXml.QDomDocumentFragment

Creates a new document fragment, that can be used to hold parts of the document, e.g. when doing complex manipulations of the document tree.

PySide6.QtXml.QDomDocument.createElement(tagName)
Parameters

tagName – str

Return type

PySide6.QtXml.QDomElement

Creates a new element called tagName that can be inserted into the DOM tree, e.g. using appendChild() .

If tagName is not a valid XML name, the behavior of this function is governed by InvalidDataPolicy .

PySide6.QtXml.QDomDocument.createElementNS(nsURI, qName)
Parameters

  • nsURI – str

  • qName – str

Return type

PySide6.QtXml.QDomElement

Creates a new element with namespace support that can be inserted into the DOM tree. The name of the element is qName and the namespace URI is nsURI. This function also sets prefix() and localName() to appropriate values (depending on qName).

If qName is an empty string, returns a null element regardless of whether the invalid data policy is set.

See also

createElement()

PySide6.QtXml.QDomDocument.createEntityReference(name)
Parameters

name – str

Return type

PySide6.QtXml.QDomEntityReference

Creates a new entity reference called name that can be inserted into the document, e.g. using appendChild() .

If name is not a valid XML name, the behavior of this function is governed by InvalidDataPolicy .

PySide6.QtXml.QDomDocument.createProcessingInstruction(target, data)
Parameters

  • target – str

  • data – str

Return type

PySide6.QtXml.QDomProcessingInstruction

Creates a new processing instruction that can be inserted into the document, e.g. using appendChild() . This function sets the target for the processing instruction to target and the data to data.

If target is not a valid XML name, or data if contains characters which cannot appear in a processing instruction, the behavior of this function is governed by InvalidDataPolicy .

PySide6.QtXml.QDomDocument.createTextNode(data)
Parameters

data – str

Return type

PySide6.QtXml.QDomText

Creates a text node for the string value that can be inserted into the document tree, e.g. using appendChild() .

If value contains characters which cannot be stored as character data of an XML document (even in the form of character references), the behavior of this function is governed by InvalidDataPolicy .

PySide6.QtXml.QDomDocument.doctype()
Return type

PySide6.QtXml.QDomDocumentType

Returns the document type of this document.

PySide6.QtXml.QDomDocument.documentElement()
Return type

PySide6.QtXml.QDomElement

Returns the root element of the document.

PySide6.QtXml.QDomDocument.elementById(elementId)
Parameters

elementId – str

Return type

PySide6.QtXml.QDomElement

Returns the element whose ID is equal to elementId. If no element with the ID was found, this function returns a null element .

Since the QDomClasses do not know which attributes are element IDs, this function returns always a null element . This may change in a future version.

PySide6.QtXml.QDomDocument.elementsByTagName(tagname)
Parameters

tagname – str

Return type

PySide6.QtXml.QDomNodeList

Returns a QDomNodeList , that contains all the elements in the document with the name tagname. The order of the node list is the order they are encountered in a preorder traversal of the element tree.

PySide6.QtXml.QDomDocument.elementsByTagNameNS(nsURI, localName)
Parameters

  • nsURI – str

  • localName – str

Return type

PySide6.QtXml.QDomNodeList

Returns a QDomNodeList that contains all the elements in the document with the local name localName and a namespace URI of nsURI. The order of the node list is the order they are encountered in a preorder traversal of the element tree.

PySide6.QtXml.QDomDocument.implementation()
Return type

PySide6.QtXml.QDomImplementation

Returns a QDomImplementation object.

PySide6.QtXml.QDomDocument.importNode(importedNode, deep)
Parameters
Return type

PySide6.QtXml.QDomNode

Imports the node importedNode from another document to this document. importedNode remains in the original document; this function creates a copy that can be used within this document.

This function returns the imported node that belongs to this document. The returned node has no parent. It is not possible to import QDomDocument and QDomDocumentType nodes. In those cases this function returns a null node .

If importedNode is a null node , a null node is returned.

If deep is true, this function imports not only the node importedNode but its whole subtree; if it is false, only the importedNode is imported. The argument deep has no effect on QDomAttr and QDomEntityReference nodes, since the descendants of QDomAttr nodes are always imported and those of QDomEntityReference nodes are never imported.

The behavior of this function is slightly different depending on the node types:

Node Type

Behavior

QDomAttr

The owner element is set to 0 and the specified flag is set to true in the generated attribute. The whole subtree of importedNode is always imported for attribute nodes: deep has no effect.

QDomDocument

Document nodes cannot be imported.

QDomDocumentFragment

If deep is true, this function imports the whole document fragment; otherwise it only generates an empty document fragment.

QDomDocumentType

Document type nodes cannot be imported.

QDomElement

Attributes for which specified() is true are also imported, other attributes are not imported. If deep is true, this function also imports the subtree of importedNode; otherwise it imports only the element node (and some attributes, see above).

QDomEntity

Entity nodes can be imported, but at the moment there is no way to use them since the document type is read-only in DOM level 2.

QDomEntityReference

Descendants of entity reference nodes are never imported: deep has no effect.

QDomNotation

Notation nodes can be imported, but at the moment there is no way to use them since the document type is read-only in DOM level 2.

QDomProcessingInstruction

The target and value of the processing instruction is copied to the new node.

QDomText

The text is copied to the new node.

QDomCDATASection

The text is copied to the new node.

QDomComment

The text is copied to the new node.

See also

setAttribute() insertBefore() insertAfter() replaceChild() removeChild() appendChild()

PySide6.QtXml.QDomDocument.setContent(text, namespaceProcessing)
Parameters

  • text – str

  • namespaceProcessing – bool

Return type

(retval, errorMsg, errorLine, errorColumn)

This is an overloaded function.

This function reads the XML document from the string text, returning true if the content was successfully parsed; otherwise returns false. Since text is already a Unicode string, no encoding detection is done.

PySide6.QtXml.QDomDocument.setContent(dev, namespaceProcessing)
Parameters
Return type

(retval, errorMsg, errorLine, errorColumn)

This is an overloaded function.

This function reads the XML document from the IO device dev, returning true if the content was successfully parsed; otherwise returns false.

Note

This method will try to open dev in read-only mode if it is not already open. In that case, the caller is responsible for calling close. This will change in Qt 7, which will no longer open dev. Applications shoul therefore open the device themselves before calling setContent .

PySide6.QtXml.QDomDocument.setContent(text)
Parameters

text – str

Return type

(retval, errorMsg, errorLine, errorColumn)

This is an overloaded function.

This function reads the XML document from the string text, returning true if the content was successfully parsed; otherwise returns false. Since text is already a Unicode string, no encoding detection is performed.

No namespace processing is performed either.

PySide6.QtXml.QDomDocument.setContent(text, namespaceProcessing)
Parameters
Return type

(retval, errorMsg, errorLine, errorColumn)

This function parses the XML document from the byte array data and sets it as the content of the document. It tries to detect the encoding of the document as required by the XML specification.

If namespaceProcessing is true, the parser recognizes namespaces in the XML file and sets the prefix name, local name and namespace URI to appropriate values. If namespaceProcessing is false, the parser does no namespace processing when it reads the XML file.

If a parse error occurs, this function returns false and the error message is placed in * errorMsg, the line number in * errorLine and the column number in * errorColumn (unless the associated pointer is set to 0); otherwise this function returns true. The various error messages are described in the QXmlParseException class documentation. Note that, if you want to display these error messages to your application’s users, they will be displayed in English unless they are explicitly translated.

If namespaceProcessing is true, the function prefix() returns a string for all elements and attributes. It returns an empty string if the element or attribute has no prefix.

Text nodes consisting only of whitespace are stripped and won’t appear in the QDomDocument . If this behavior is not desired, one can use the overload that allows a QXmlReader to be supplied.

If namespaceProcessing is false, the functions prefix() , localName() and namespaceURI() return an empty string.

Entity references are handled as follows:

  • References to internal general entities and character entities occurring in the content are included. The result is a QDomText node with the references replaced by their corresponding entity values.

  • References to parameter entities occurring in the internal subset are included. The result is a QDomDocumentType node which contains entity and notation declarations with the references replaced by their corresponding entity values.

  • Any general parsed entity reference which is not defined in the internal subset and which occurs in the content is represented as a QDomEntityReference node.

  • Any parsed entity reference which is not defined in the internal subset and which occurs outside of the content is replaced with an empty string.

  • Any unparsed entity reference is replaced with an empty string.

See also

namespaceURI() localName() prefix() isNull() isEmpty()

PySide6.QtXml.QDomDocument.setContent(reader, namespaceProcessing[, errorMsg=None[, errorLine=None[, errorColumn=None]]])
Parameters
Return type

bool

This is an overloaded function.

This function reads the XML document from the QXmlStreamReader reader and parses it. Returns true if the content was successfully parsed; otherwise returns false.

If namespaceProcessing is true, the parser recognizes namespaces in the XML file and sets the prefix name, local name and namespace URI to appropriate values. If namespaceProcessing is false, the parser does no namespace processing when it reads the XML file.

If a parse error occurs, the error message is placed in * errorMsg, the line number in * errorLine and the column number in * errorColumn (unless the associated pointer is set to 0).

See also

QXmlStreamReader

PySide6.QtXml.QDomDocument.setContent(dev)
Parameters

dev – PySide6.QtCore.QIODevice

Return type

(retval, errorMsg, errorLine, errorColumn)

This is an overloaded function.

This function reads the XML document from the IO device dev, returning true if the content was successfully parsed; otherwise returns false.

No namespace processing is performed.

PySide6.QtXml.QDomDocument.setContent(text)
Parameters

text – PySide6.QtCore.QByteArray

Return type

(retval, errorMsg, errorLine, errorColumn)

This is an overloaded function.

This function reads the XML document from the byte array buffer, returning true if the content was successfully parsed; otherwise returns false.

No namespace processing is performed.

PySide6.QtXml.QDomDocument.toByteArray([arg__1=1])
Parameters

arg__1 – int

Return type

PySide6.QtCore.QByteArray

Converts the parsed document back to its textual representation and returns a QByteArray containing the data encoded as UTF-8.

This function uses indent as the amount of space to indent subelements.

See also

toString()

PySide6.QtXml.QDomDocument.toString([arg__1=1])
Parameters

arg__1 – int

Return type

str

Converts the parsed document back to its textual representation.

This function uses indent as the amount of space to indent subelements.

If indent is -1, no whitespace at all is added.