New in version 2.0.
xml.dom.minidom is a light-weight implementation of the Document Object Model interface. It is intended to be simpler than the full DOM and also significantly smaller.
DOM applications typically start by parsing some XML into a DOM. With xml.dom.minidom, this is done through the parse functions:
from xml.dom.minidom import parse, parseString
dom1 = parse('c:\\temp\\mydata.xml') # parse an XML file by name
datasource = open('c:\\temp\\mydata.xml')
dom2 = parse(datasource) # parse an open file
dom3 = parseString('<myxml>Some data<empty/> some more data</myxml>')
The parse() function can take either a filename or an open file object.
Return a Document from the given input. filename_or_file may be either a file name, or a file-like object. parser, if given, must be a SAX2 parser object. This function will change the document handler of the parser and activate namespace support; other parser configuration (like setting an entity resolver) must have been done in advance.
If you have XML in a string, you can use the parseString() function instead:
Return a Document that represents the string. This method creates a StringIO object for the string and passes that on to parse().
Both functions return a Document object representing the content of the document.
What the parse() and parseString() functions do is connect an XML parser with a “DOM builder” that can accept parse events from any SAX parser and convert them into a DOM tree. The name of the functions are perhaps misleading, but are easy to grasp when learning the interfaces. The parsing of the document will be completed before these functions return; it’s simply that these functions do not provide a parser implementation themselves.
You can also create a Document by calling a method on a “DOM Implementation” object. You can get this object either by calling the getDOMImplementation() function in the xml.dom package or the xml.dom.minidom module. Using the implementation from the xml.dom.minidom module will always return a Document instance from the minidom implementation, while the version from xml.dom may provide an alternate implementation (this is likely if you have the PyXML package installed). Once you have a Document, you can add child nodes to it to populate the DOM:
from xml.dom.minidom import getDOMImplementation
impl = getDOMImplementation()
newdoc = impl.createDocument(None, "some_tag", None)
top_element = newdoc.documentElement
text = newdoc.createTextNode('Some textual content.')
top_element.appendChild(text)
Once you have a DOM document object, you can access the parts of your XML document through its properties and methods. These properties are defined in the DOM specification. The main property of the document object is the documentElement property. It gives you the main element in the XML document: the one that holds all others. Here is an example program:
dom3 = parseString("<myxml>Some data</myxml>")
assert dom3.documentElement.tagName == "myxml"
When you are finished with a DOM tree, you may optionally call the unlink() method to encourage early cleanup of the now-unneeded objects. unlink() is a xml.dom.minidom-specific extension to the DOM API that renders the node and its descendants are essentially useless. Otherwise, Python’s garbage collector will eventually take care of the objects in the tree.
See also
The definition of the DOM API for Python is given as part of the xml.dom module documentation. This section lists the differences between the API and xml.dom.minidom.
Break internal references within the DOM so that it will be garbage collected on versions of Python without cyclic GC. Even when cyclic GC is available, using this can make large amounts of memory available sooner, so calling this on DOM objects as soon as they are no longer needed is good practice. This only needs to be called on the Document object, but may be called on child nodes to discard children of that node.
Write XML to the writer object. The writer should have a write() method which matches that of the file object interface. The indent parameter is the indentation of the current node. The addindent parameter is the incremental indentation to use for subnodes of the current one. The newl parameter specifies the string to use to terminate newlines.
Changed in version 2.1: The optional keyword parameters indent, addindent, and newl were added to support pretty output.
Changed in version 2.3: For the Document node, an additional keyword argument encoding can be used to specify the encoding field of the XML header.
Return the XML that the DOM represents as a string.
With no argument, the XML header does not specify an encoding, and the result is Unicode string if the default encoding cannot represent all characters in the document. Encoding this string in an encoding other than UTF-8 is likely incorrect, since UTF-8 is the default encoding of XML.
With an explicit encoding [1] argument, the result is a byte string in the specified encoding. It is recommended that this argument is always specified. To avoid UnicodeError exceptions in case of unrepresentable text data, the encoding argument should be specified as “utf-8”.
Changed in version 2.3: the encoding argument was introduced; see writexml().
Return a pretty-printed version of the document. indent specifies the indentation string and defaults to a tabulator; newl specifies the string emitted at the end of each line and defaults to \n.
New in version 2.1.
Changed in version 2.3: the encoding argument was introduced; see writexml().
The following standard DOM methods have special considerations with xml.dom.minidom:
Although this method was present in the version of xml.dom.minidom packaged with Python 2.0, it was seriously broken. This has been corrected for subsequent releases.
This example program is a fairly realistic example of a simple program. In this particular case, we do not take much advantage of the flexibility of the DOM.
The xml.dom.minidom module is essentially a DOM 1.0-compatible DOM with some DOM 2 features (primarily namespace features).
Usage of the DOM interface in Python is straight-forward. The following mapping rules apply:
The following interfaces have no implementation in xml.dom.minidom:
Most of these reflect information in the XML document that is not of general utility to most DOM users.
Footnotes
| [1] | The encoding string included in XML output should conform to the appropriate standards. For example, “UTF-8” is valid, but “UTF8” is not. See http://www.w3.org/TR/2006/REC-xml11-20060816/#NT-EncodingDecl and http://www.iana.org/assignments/character-sets . |