twisted.words.xish.domish.Element : API documentation

Represents an XML element node.

An Element contains a series of attributes (name/value pairs), content (character data), and other child Element objects. When building a document with markup (such as HTML or XML), use this object as the starting point.

Element objects fully support XML Namespaces. The fully qualified name of the XML Element it represents is stored in the uri and name attributes, where uri holds the namespace URI. There is also a default namespace, for child elements. This is stored in the defaultUri attribute. Note that '' means the empty namespace.

Serialization of Elements through toXml() will use these attributes for generating proper serialized XML. When both uri and defaultUri are not None in the Element and all of its descendents, serialization proceeds as expected:

>>> from twisted.words.xish import domish
>>> root = domish.Element(('myns', 'root'))
>>> root.addElement('child', content='test')
<twisted.words.xish.domish.Element object at 0x83002ac>
>>> root.toXml()
u"<root xmlns='myns'><child>test</child></root>"

For partial serialization, needed for streaming XML, a special value for namespace URIs can be used: None.

Using None as the value for uri means: this element is in whatever namespace inherited by the closest logical ancestor when the complete XML document has been serialized. The serialized start tag will have a non-prefixed name, and no xmlns declaration will be generated.

Similarly, None for defaultUri means: the default namespace for my child elements is inherited from the logical ancestors of this element, when the complete XML document has been serialized.

To illustrate, an example from a Jabber stream. Assume the start tag of the root element of the stream has already been serialized, along with several complete child elements, and sent off, looking like this:

 <stream:stream xmlns:stream='http://etherx.jabber.org/streams'
                xmlns='jabber:client' to='example.com'>
   ...

Now suppose we want to send a complete element represented by an object message created like:

>>> message = domish.Element((None, 'message'))
>>> message['to'] = 'user@example.com'
>>> message.addElement('body', content='Hi!')
<twisted.words.xish.domish.Element object at 0x8276e8c>
>>> message.toXml()
u"<message to='user@example.com'><body>Hi!</body></message>"

As, you can see, this XML snippet has no xmlns declaration. When sent off, it inherits the jabber:client namespace from the root element. Note that this renders the same as using '' instead of None:

>>> presence = domish.Element(('', 'presence'))
>>> presence.toXml()
u"<presence/>"

However, if this object has a parent defined, the difference becomes clear:

>>> child = message.addElement(('http://example.com/', 'envelope'))
>>> child.addChild(presence)
<twisted.words.xish.domish.Element object at 0x8276fac>
>>> message.toXml()
u"<message to='user@example.com'><body>Hi!</body><envelope xmlns='http://example.com/'><presence xmlns=''/></envelope></message>"

As, you can see, the <presence/> element is now in the empty namespace, not in the default namespace of the parent or the streams'.

Instance Variable	uri	URI of this Element's name (type: `unicode` or None)
Instance Variable	name	Name of this Element (type: `unicode`)
Instance Variable	defaultUri	URI this Element exists within (type: `unicode` or None)
Instance Variable	children	List of child Elements and content (type: `list`)
Instance Variable	parent	Reference to the parent Element, if any. (type: `Element`)
Instance Variable	attributes	Dictionary of attributes associated with this Element. (type: `dict`)
Instance Variable	localPrefixes	Dictionary of namespace declarations on this element. The key is the prefix to bind the namespace uri to. (type: `dict`)
Method	__init__	No summary
Method	__getattr__	Undocumented
Method	__getitem__	Undocumented
Method	__delitem__	Undocumented
Method	__setitem__	Undocumented
Method	__str__	Retrieve the first CData (content) node
Method	getAttribute	Retrieve the value of attribname, if it exists
Method	hasAttribute	Determine if the specified attribute exists
Method	compareAttribute	Safely compare the value of an attribute against a provided value.
Method	swapAttributeValues	Swap the values of two attribute.
Method	addChild	Add a child to this Element.
Method	addContent	Add some text data to this Element.
Method	addElement	Create an element and add as child.
Method	addRawXml	Add a pre-serialized chunk o' XML as a child of this Element.
Method	addUniqueId	Add a unique (across a given Python session) id attribute to this Element.
Method	elements	Iterate across all children of this Element that are Elements.
Method	toXml	Serialize this Element and all children to a string.
Method	firstChildElement	Undocumented
Method	_dqa	Dequalify an attribute key as needed

def addElement(self, name, defaultUri=None, content=None): (source)

from twisted.words.xish.domish.IElement

Create an element and add as child.

The new element is added to this element as a child, and will have this element as its parent.

Parameters	name	element name. This can be either a `unicode` object that contains the local name, or a tuple of (uri, local_name) for a fully qualified name. In the former case, the namespace URI is inherited from this element. (type: `unicode` or `tuple` of (`unicode`, `unicode`))
	defaultUri	default namespace URI for child elements. If `None`, this is inherited from this element. (type: `unicode`)
	content	text contained by the new element. (type: `unicode`)
Returns	the created element (type: object providing `IElement`)

Parameters	qname	Tuple of (uri, name)
	defaultUri	The default URI of the element; defaults to the URI specified in `qname`
	attribs	Dictionary of attributes
	localPrefixes	Dictionary of namespace declarations on this element. The key is the prefix to bind the namespace uri to.

Parameters	uri	Optional element URI. (type: `unicode`)
	name	Optional element name. (type: `unicode`)
Returns	Iterator that yields objects implementing `IElement`.

t.w.x.d.Element(object) : class documentation