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4DOM Extensions
4DOM Extensions
These are utility classes and functions that provide capabilities not yet specified in the DOM spec. Some of these facilities, such as factories and readers are expected to be specified in later levels of the DOM, so we try to keep our proprietary interfaces simple for now so that you can more painlessly migrate when relevant standards emerge.
See the demo directory for examples exercising many of these extensions.
Reading
The Reader package allows you to parse source strings in XML and HTML into DOM trees. You select a reader module according to the nature of your input. The readers that come with 4DOM are as follows:
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PyExpat
-
Read XML using pyexpat from PyXML. Does not support validation.
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HtmlLib
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Read HTML using Python's htmllib.
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Sax2
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Read XML using the PyXML SAX2 package. DTD validation is option.
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Sax (deprecated)
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Read XML using the PyXML SAX package. DTD validation is option.
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Sgmlop
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Read XML using Sgmlop from PyXML. Does not support validation.
The following two examples illustrate using PyExpat and HtmlLib readers. Replace with the appropriate module and use in your own code.
# Parse XML using pyexpat
from xml.dom.ext.reader import PyExpat
reader = PyExpat.Reader()
xml_doc = reader.fromStream(stream)
#Parse HTML using htmllib
from xml.dom.ext.reader import HtmlLib
reader = HtmlLib.Reader()
html_doc = reader.fromStream(stream)
Module PyExpat
Parse XML using pyexpat
Module Summary
Classes
|
Class Summary
|
Reader
|
Reusable utility to read XML documents. |
Class Reader
Reusable utility to read XML documents.
|
Method Summary
|
fromStream
|
return a 4DOM node from the given stream |
fromString
|
return a 4DOM node from the given string |
fromUri
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return a 4DOM node from the given uri |
fromStream
fromStream(stream, ownerDoc)
return a 4DOM node from the given stream
Parameters
-
stream
of type
Python file object
-
The stream to be read for XML text
-
ownerDoc
of type
xml.dom.Document.Document
-
A document to be used as owner of all the created nodes. If None, a new document instance is created for the nodes. Default is None.
Return Value
-
-
a new document instance, or if the ownerDoc argument was not None, a document fragment. In either case, the returned node roots the created XML tree.
fromString
fromString(xmlString, ownerDoc)
return a 4DOM node from the given string
Parameters
-
xmlString
of type
string or unicode object
-
The string to be parsed for XML text
-
ownerDoc
of type
xml.dom.Document.Document
-
A document to be used as owner of all the created nodes. If None, a new document instance is created for the nodes. Default is None.
Return Value
-
-
a new document instance, or if the ownerDoc argument was not None, a document fragment. In either case, the returned node roots the created XML tree.
fromUri
fromUri(uri, ownerDoc)
return a 4DOM node from the given uri
Parameters
-
uri
of type
Python file object
-
The uri from which XML text is to be retrieved
-
ownerDoc
of type
xml.dom.Document.Document
-
A document to be used as owner of all the created nodes. If None, a new document instance is created for the nodes. Default is None.
Return Value
-
-
a new document instance, or if the ownerDoc argument was not None, a document fragment. In either case, the returned node roots the created XML tree.
Module HtmlLib
Parse HTML using htmllib
Module Summary
Classes
|
Class Summary
|
Reader
|
Reusable utility to read HTML documents. |
Class Reader
Reusable utility to read HTML documents.
|
Method Summary
|
fromStream
|
return a 4DOM node from the given stream |
fromString
|
return a 4DOM node from the given string |
fromUri
|
return a 4DOM node from the given uri |
fromStream
fromStream(stream, ownerDoc, charset)
return a 4DOM node from the given stream
Parameters
-
stream
of type
Python file object
-
The stream to be read for HTML text
-
ownerDoc
of type
xml.dom.Document.Document
-
A document to be used as owner of all the created nodes. If None, a new document instance is created for the nodes. Default is None.
-
charset
of type
string
-
The character set of the HTML text. If None or empty string, the default is ISO-8859-1. Default is empty string.
Return Value
-
-
a new document instance, or if the ownerDoc argument was not None, a document fragment. In either case, the returned node roots the created HTML tree.
fromString
fromString(htmlString, ownerDoc, charset)
return a 4DOM node from the given string
Parameters
-
htmlString
of type
string or unicode object
-
The string to be parsed for HTML text
-
ownerDoc
of type
xml.dom.Document.Document
-
A document to be used as owner of all the created nodes. If None, a new document instance is created for the nodes. Default is None.
-
charset
of type
string
-
The character set of the HTML text. If None or empty string, the default is ISO-8859-1. Default is empty string.
Return Value
-
-
a new document instance, or if the ownerDoc argument was not None, a document fragment. In either case, the returned node roots the created HTML tree.
fromUri
fromUri(uri, ownerDoc, charset)
return a 4DOM node from the given uri
Parameters
-
uri
of type
Python file object
-
The uri from which HTML text is to be retrieved
-
ownerDoc
of type
xml.dom.Document.Document
-
A document to be used as owner of all the created nodes. If None, a new document instance is created for the nodes. Default is None.
-
charset
of type
string
-
The character set of the HTML text. If None or empty string, the default is ISO-8859-1. Default is empty string.
Return Value
-
-
a new document instance, or if the ownerDoc argument was not None, a document fragment. In either case, the returned node roots the created HTML tree.
Printing/Writing
The Printer module allows you to write a text representation of DOM nodes
to an output stream, including stdout. Note that limitations in the
SAX interface used to parse in XML files, and in the DOM spec itself make
it impossible at this point to handle an unchanged "round trip".
That is, if you use the builder to build a DOM node from text and then
use the Printer to turn it back to text, there may be differences;
some may be significant.
The easiest way to use the Printer module is through the front-end functions in the xml.dom.ext package.
xml.dom.ext.Print
xml.dom.ext.Print(root, stream, encoding)
Render the DOM tree to text with no special formatting.
Parameters
-
root
of type
xml.dom.Node
-
The node to be printed, with all its children recursively.
-
stream
of type
output stream
-
The output stream. Note: can be a StringIO object if you want to generate a string instead. Default is sys.stdout.
-
encoding
of type
string
-
The character encoding to use for output. Default is 'UTF-8'.
Return Value
None
xml.dom.ext.PrettyPrint
xml.dom.ext.PrettyPrint(root, stream, encoding, indent, width, preserveElements)
Render the DOM tree to text, with added indentation and new-lines for enhanced readability.
Parameters
-
root
of type
xml.dom.Node
-
The node to be pretty-printed, with all its children recursively.
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stream
of type
output stream
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The output stream. Note: can be a StringIO object if you want to generate a string instead. Default is sys.stdout.
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encoding
of type
string
-
The character encoding to use for output. Default is 'UTF-8'.
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indent
of type
string
-
The amount by which nested constructs are indented when printed on a fresh line. Default is '\t'.
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width
of type
positive integer
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The width of the output console. Used to make
line-break decisions. Default is 80.
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preserveElements
of type
list of strings, each of which is an SGML generic identifier.
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Specifes elements in which white-space shouldn't be added. Note that white-space is never added to in-line elements in an HTMLDocument. Default is None.
Return Value
None
xml.dom.ext.XHtmlPrint
xml.dom.ext.XHtmlPrint(root, stream, encoding)
Render an HTML DOM tree as XHTML with no special indentation or formatting.
Parameters
-
root
of type
xml.dom.Node
-
The HTML node to be printed, with all its children recursively.
-
stream
of type
output stream
-
The output stream. Note: can be a StringIO object if you want to generate a string instead. Default is sys.stdout.
-
encoding
of type
string
-
The character encoding to use for output. Default is 'UTF-8'.
Return Value
None
xml.dom.ext.XHtmlPrettyPrint
xml.dom.ext.XHtmlPrettyPrint(root, stream, encoding, indent, width, preserveElements)
Render an HTML DOM tree to text, with added indentation and new-lines for enhanced readability.
Parameters
-
root
of type
xml.dom.Node
-
The node to be pretty-printed, with all its children recursively.
-
stream
of type
output stream
-
The output stream. Note: can be a StringIO object if you want to generate a string instead. Default is sys.stdout.
-
encoding
of type
string
-
The character encoding to use for output. Default is 'UTF-8'.
-
indent
of type
string
-
The amount by which nested constructs are indented when printed on a fresh line. Default is '\t'.
-
width
of type
positive integer
-
The width of the output console. Used to make
line-break decisions. Default is 80.
-
preserveElements
of type
list of strings, each of which is an SGML generic identifier.
-
Specifes elements in which white-space shouldn't be added. Note that white-space is never added to in-line elements in an HTMLDocument. Default is None.
Return Value
None
Miscellaneous
xml.dom.ext.NodeTypeToInterface
xml.dom.ext.NodeTypeToInterface(nodeType)
Look up a node type (as returned from getNodeType()) and returns a corresponding interface name.
Parameters
-
nodeType
of type
One of the integers defined as node types in xml.dom.Node
-
The node type to look up.
Return Value
-
string
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Name of corresponding DOM interface from spec.
xml.dom.ext.StripHtml
xml.dom.ext.StripHtml(startNode, preserveElements)
Strips extraneous white-space from an HTML DOM tree.
Parameters
-
startNode
of type
xml.dom.Node
-
The node to be stripped, with all its children recursively.
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preserveElements
of type
list of strings, each of which is an SGML generic identifier, or None to indicate an empty list.
-
Specifes elements from which white-space shouldn't be stripped. Note that white-space is never stripped from in-line elements in an HTMLDocument. Default is None.
Return Value
-
xml.dom.Node
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The startNode with descendant ignorable white-space stripped.
xml.dom.ext.StripXml
xml.dom.ext.StripXml(startNode, preserveElements)
Strips extraneous white-space from an XML DOM tree. Takes xml:space attributes into account.
Parameters
-
startNode
of type
xml.dom.Node
-
The node to be stripped, with all its children recursively.
-
preserveElements
of type
list of strings, each of which is an SGML generic identifier, or None to indicate an empty list.
-
Specifes elements from which white-space shouldn't be stripped. Default is None.
Return Value
-
xml.dom.Node
-
The startNode with descendant ignorable white-space stripped.
xml.dom.ext.GetElementById
xml.dom.ext.GetElementById(startNode, targetId)
Returns the element node whose "ID" attribute is as given.
Parameters
-
startNode
of type
xml.dom.Node
-
The node whose descendants are to be searched.
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targetId
of type
string conforming to XML ID type
-
The XML ID to find.
Return Value
-
xml.dom.Element
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The elemtn with the given ID, or None to indicate no match.
xml.dom.ext.GetAllNs
xml.dom.ext.GetAllNs(node)
Returns all the namespaces in effect on the given node, including the default namespace and the xml namespace.
Parameters
-
node
of type
xml.dom.Node
-
The node for which all in-scope namespaces are returned.
Return Value
-
doctionary
-
Dictionary mapping all in-scope namespaces to URIs, with '' as prefix for the default namespace.
xml.dom.ext.XmlSpaceState
xml.dom.ext.XmlSpaceState(node)
Determines whether the xml:space state at a given node is "preserve" or "default" (See the XML 1.0 spec).
Parameters
-
node
of type
xml.dom.Node
-
The node whose space state is to be found.
Return Value
-
string
-
"preserve" or "default".
xml.dom.ext.SplitQName
xml.dom.ext.SplitQName(qname)
Splits a valid QName from the XML Namespaces 1.0 spec into prefix and suffix (the local name in the case of element and attribute names, and the declared prefix in the case of namespace declarations.
Parameters
-
qname
of type
string matching QName production in XML Namespaces 1.0 spec
-
The name to be split.
Return Value
-
tuple with 2 items.
-
a tuple of the form (prefix, suffix). If there is exactly one colon in the qname, prefix is the part before and suffix the part after the colon. Otherwise prefix is '' and suffix is the entire input string.
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