QXmlStreamWriter露

PyQt5.QtCore.QXmlStreamWriter

Description露

The QXmlStreamWriter class provides an XML writer with a simple streaming API.

QXmlStreamWriter is the counterpart to QXmlStreamReader for writing XML. Like its related class, it operates on a QIODevice specified with setDevice(). The API is simple and straightforward: for every XML token or event you want to write, the writer provides a specialized function.

You start a document with writeStartDocument() and end it with writeEndDocument(). This will implicitly close all remaining open tags.

Element tags are opened with writeStartElement() followed by writeAttribute() or writeAttributes(), element content, and then writeEndElement(). A shorter form writeEmptyElement() can be used to write empty elements, followed by writeAttributes().

Element content consists of either characters, entity references or nested elements. It is written with writeCharacters(), which also takes care of escaping all forbidden characters and character sequences, writeEntityReference(), or subsequent calls to writeStartElement(). A convenience method writeTextElement() can be used for writing terminal elements that contain nothing but text.

The following abridged code snippet shows the basic use of the class to write formatted XML with indentation:

#     QXmlStreamWriter stream(&output);
#     stream.setAutoFormatting(true);
#     stream.writeStartDocument();

#     stream.writeStartElement("bookmark");
#     stream.writeAttribute("href", "http://qt-project.org/");
#     stream.writeTextElement("title", "Qt Project");
#     stream.writeEndElement(); // bookmark

#     stream.writeEndDocument();

QXmlStreamWriter takes care of prefixing namespaces, all you have to do is specify the namespaceUri when writing elements or attributes. If you must conform to certain prefixes, you can force the writer to use them by declaring the namespaces manually with either writeNamespace() or writeDefaultNamespace(). Alternatively, you can bypass the stream writer鈥檚 namespace support and use overloaded methods that take a qualified name instead. The namespace http://www.w3.org/XML/1998/namespace is implicit and mapped to the prefix xml.

The stream writer can automatically format the generated XML data by adding line-breaks and indentation to empty sections between elements, making the XML data more readable for humans and easier to work with for most source code management systems. The feature can be turned on with the autoFormatting() property, and customized with the autoFormattingIndent() property.

Other functions are writeCDATA(), writeComment(), writeProcessingInstruction(), and writeDTD(). Chaining of XML streams is supported with writeCurrentToken().

By default, QXmlStreamWriter encodes XML in UTF-8. Different encodings can be enforced using setCodec().

If an error occurs while writing to the underlying device, hasError() starts returning true and subsequent writes are ignored.

The QXmlStream Bookmarks Example illustrates how to use a stream writer to write an XML bookmark file (XBEL) that was previously read in by a QXmlStreamReader.

Methods露

__init__()

Constructs a stream writer.

See also

setDevice().

__init__(QIODevice)

Constructs a stream writer that writes into device;

__init__(Union[QByteArray, bytes, bytearray])

Constructs a stream writer that writes into array. This is the same as creating an xml writer that operates on a QBuffer device which in turn operates on array.

autoFormatting() → bool

Returns true if auto formattting is enabled, otherwise false.

See also

setAutoFormatting().

autoFormattingIndent() → int

See also

setAutoFormattingIndent().

codec() → QTextCodec

Returns the codec that is currently assigned to the stream.

See also

setCodec().

device() → QIODevice

Returns the current device associated with the QXmlStreamWriter, or 0 if no device has been assigned.

See also

setDevice().

hasError() → bool

Returns true if writing failed.

This can happen if the stream failed to write to the underlying device or if the data to be written contained invalid characters.

The error status is never reset. Writes happening after the error occurred may be ignored, even if the error condition is cleared.

setAutoFormatting(bool)

Enables auto formatting if enable is true, otherwise disables it.

The default value is false.

See also

autoFormatting().

setAutoFormattingIndent(int)

See also

autoFormattingIndent().

setCodec(QTextCodec)

Sets the codec for this stream to codec. The codec is used for encoding any data that is written. By default, QXmlStreamWriter uses UTF-8.

The encoding information is stored in the initial xml tag which gets written when you call writeStartDocument(). Call this function before calling writeStartDocument().

Note: When writing the XML to a QString, the codec information is ignored and the XML header will not include any encoding information, since all QStrings are UTF-16. If you later convert the QString to an 8-bit format, you must arrange for the encoding information to be transmitted out-of-band.

See also

codec().

setCodec(str)

Sets the codec for this stream to the QTextCodec for the encoding specified by codecName. Common values for codecName include 鈥淚SO 8859-1鈥, 鈥淯TF-8鈥, and 鈥淯TF-16鈥. If the encoding isn鈥檛 recognized, nothing happens.

Note: When writing the XML to a QString, the codec information is ignored and the XML header will not include any encoding information, since all QStrings are UTF-16. If you later convert the QString to an 8-bit format, you must arrange for the encoding information to be transmitted out-of-band.

See also

codecForName().

setDevice(QIODevice)

Sets the current device to device. If you want the stream to write into a QByteArray, you can create a QBuffer device.

See also

device().

writeAttribute(QXmlStreamAttribute)

This is an overloaded function.

Writes the attribute.

This function can only be called after writeStartElement() before any content is written, or after writeEmptyElement().

writeAttribute(str, str)

This is an overloaded function.

Writes an attribute with qualifiedName and value.

This function can only be called after writeStartElement() before any content is written, or after writeEmptyElement().

writeAttribute(str, str, str)

Writes an attribute with name and value, prefixed for the specified namespaceUri. If the namespace has not been declared yet, QXmlStreamWriter will generate a namespace declaration for it.

This function can only be called after writeStartElement() before any content is written, or after writeEmptyElement().

writeAttributes(QXmlStreamAttributes)

Writes the attribute vector attributes. If a namespace referenced in an attribute not been declared yet, QXmlStreamWriter will generate a namespace declaration for it.

This function can only be called after writeStartElement() before any content is written, or after writeEmptyElement().

See also

writeAttribute(), writeNamespace().

writeCDATA(str)

Writes text as CDATA section. If text contains the forbidden character sequence 鈥淽]>鈥, it is split into different CDATA sections.

This function mainly exists for completeness. Normally you should not need use it, because writeCharacters() automatically escapes all non-content characters.

writeCharacters(str)

Writes text. The characters 鈥<鈥, 鈥&鈥, and 鈥溾濃 are escaped as entity references 鈥&lt;鈥, 鈥&amp;, and 鈥&quot;鈥. To avoid the forbidden sequence 鈥淽]>鈥, 鈥>鈥 is also escaped as 鈥&gt;鈥.

See also

writeEntityReference().

writeComment(str)

Writes text as XML comment, where text must not contain the forbidden sequence 鈥溾撯 or end with 鈥-鈥. Note that XML does not provide any way to escape 鈥-鈥 in a comment.

writeCurrentToken(QXmlStreamReader)

Writes the current state of the reader. All possible valid states are supported.

The purpose of this function is to support chained processing of XML data.

See also

tokenType().

writeDefaultNamespace(str)

Writes a default namespace declaration for namespaceUri.

If writeStartElement() or writeEmptyElement() was called, the declaration applies to the current element; otherwise it applies to the next child element.

Note that the namespaces http://www.w3.org/XML/1998/namespace (bound to xmlns) and http://www.w3.org/2000/xmlns/ (bound to xml) by definition cannot be declared as default.

writeDTD(str)

Writes a DTD section. The dtd represents the entire doctypedecl production from the XML 1.0 specification.

writeEmptyElement(str)

This is an overloaded function.

Writes an empty element with qualified name qualifiedName. Subsequent calls to writeAttribute() will add attributes to this element.

writeEmptyElement(str, str)

Writes an empty element with name, prefixed for the specified namespaceUri. If the namespace has not been declared, QXmlStreamWriter will generate a namespace declaration for it. Subsequent calls to writeAttribute() will add attributes to this element.

See also

writeNamespace().

writeEndDocument()

Closes all remaining open start elements and writes a newline.

See also

writeStartDocument().

writeEndElement()

Closes the previous start element.

See also

writeStartElement().

writeEntityReference(str)

Writes the entity reference name to the stream, as 鈥&name;鈥.

writeNamespace(str, prefix: str = '')

Writes a namespace declaration for namespaceUri with prefix. If prefix is empty, QXmlStreamWriter assigns a unique prefix consisting of the letter 鈥榥鈥 followed by a number.

If writeStartElement() or writeEmptyElement() was called, the declaration applies to the current element; otherwise it applies to the next child element.

Note that the prefix xml is both predefined and reserved for http://www.w3.org/XML/1998/namespace, which in turn cannot be bound to any other prefix. The prefix xmlns and its URI http://www.w3.org/2000/xmlns/ are used for the namespace mechanism itself and thus completely forbidden in declarations.

writeProcessingInstruction(str, data: str = '')

Writes an XML processing instruction with target and data, where data must not contain the sequence 鈥?>鈥.

writeStartDocument()

This is an overloaded function.

Writes a document start with XML version number 鈥1.0鈥. This also writes the encoding information.

See also

writeEndDocument(), setCodec().

writeStartDocument(str)

Writes a document start with the XML version number version.

See also

writeEndDocument().

writeStartDocument(str, bool)

Writes a document start with the XML version number version and a standalone attribute standalone.

See also

writeEndDocument().

writeStartElement(str)

This is an overloaded function.

Writes a start element with qualifiedName. Subsequent calls to writeAttribute() will add attributes to this element.

See also

writeEndElement(), writeEmptyElement().

writeStartElement(str, str)

Writes a start element with name, prefixed for the specified namespaceUri. If the namespace has not been declared yet, QXmlStreamWriter will generate a namespace declaration for it. Subsequent calls to writeAttribute() will add attributes to this element.

See also

writeNamespace(), writeEndElement(), writeEmptyElement().

writeTextElement(str, str)

This is an overloaded function.

Writes a text element with qualifiedName and text.

This is a convenience function equivalent to:

#         writeStartElement(qualifiedName);
#         writeCharacters(text);
#         writeEndElement();
writeTextElement(str, str, str)

Writes a text element with name, prefixed for the specified namespaceUri, and text. If the namespace has not been declared, QXmlStreamWriter will generate a namespace declaration for it.

This is a convenience function equivalent to:

#         writeStartElement(namespaceUri, name);
#         writeCharacters(text);
#         writeEndElement();