twisted.words.xish.domish.Element(object) class documentationtwisted.words.xish.domish
(View In Hierarchy)
Known subclasses: twisted.words.protocols.jabber.client.IQ, twisted.words.protocols.jabber.xmlstream.IQ
Implements interfaces: twisted.words.xish.domish.IElement
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 | __unicode__ | Retrieve the first CData (content) node |
| Method | __bytes__ | Retrieve the first character data node as UTF-8 bytes. |
| 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 |
dict)
| 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. |
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) | |
Iterate across all children of this Element that are Elements.
Returns a generator over the child elements. If both the
uri and name parameters are set, the returned
generator will only yield on elements matching the qualified name.
| Parameters | uri | Optional element URI. (type: unicode) |
| name | Optional element name. (type: unicode) | |
| Returns | Iterator that yields objects implementing IElement. | |