xml.dom.minidom --- 最小的 DOM 實作¶xml.dom.minidom is a minimal implementation of the Document Object
Model interface, with an API similar to that in other languages. It is intended
to be simpler than the full DOM and also significantly smaller. Users who are
not already proficient with the DOM should consider using the
xml.etree.ElementTree module for their XML processing instead.
警告
The xml.dom.minidom module is not secure against
maliciously constructed data. If you need to parse untrusted or
unauthenticated data see XML 漏洞.
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 an
io.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. 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 an xml.dom.minidom-specific
extension to the DOM API that renders the node and its descendants
essentially useless. Otherwise, Python's garbage collector will
eventually take care of the objects in the tree.
也參考
The W3C recommendation for the DOM supported by xml.dom.minidom.
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.
You can avoid calling this method explicitly by using the with
statement. The following code will automatically unlink dom when the
with block is exited:
with xml.dom.minidom.parse(datasource) as dom:
... # Work with dom.
Write XML to the writer object. The writer receives texts but not bytes as input,
it 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.
For the Document node, an additional keyword argument encoding can
be used to specify the encoding field of the XML header.
Similarly, explicitly stating the standalone argument causes the
standalone document declarations to be added to the prologue of the XML
document.
If the value is set to True, standalone="yes" is added,
otherwise it is set to "no".
Not stating the argument will omit the declaration from the document.
在 3.8 版的變更: The writexml() method now preserves the attribute order specified
by the user.
在 3.9 版的變更: 新增 standalone 參數。
Return a string or byte string containing the XML represented by the DOM node.
With an explicit encoding [1] argument, the result is a byte string in the specified encoding. With no encoding argument, the result is a Unicode string, and the XML declaration in the resulting string does not specify an encoding. Encoding this string in an encoding other than UTF-8 is likely incorrect, since UTF-8 is the default encoding of XML.
The standalone argument behaves exactly as in writexml().
在 3.8 版的變更: The toxml() method now preserves the attribute order specified
by the user.
在 3.9 版的變更: 新增 standalone 參數。
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.
The encoding argument behaves like the corresponding argument of
toxml().
The standalone argument behaves exactly as in writexml().
在 3.8 版的變更: The toprettyxml() method now preserves the attribute order specified
by the user.
在 3.9 版的變更: 新增 standalone 參數。
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.
import xml.dom.minidom
document = """\
<slideshow>
<title>Demo slideshow</title>
<slide><title>Slide title</title>
<point>This is a demo</point>
<point>Of a program for processing slides</point>
</slide>
<slide><title>Another demo slide</title>
<point>It is important</point>
<point>To have more than</point>
<point>one slide</point>
</slide>
</slideshow>
"""
dom = xml.dom.minidom.parseString(document)
def getText(nodelist):
rc = []
for node in nodelist:
if node.nodeType == node.TEXT_NODE:
rc.append(node.data)
return ''.join(rc)
def handleSlideshow(slideshow):
print("<html>")
handleSlideshowTitle(slideshow.getElementsByTagName("title")[0])
slides = slideshow.getElementsByTagName("slide")
handleToc(slides)
handleSlides(slides)
print("</html>")
def handleSlides(slides):
for slide in slides:
handleSlide(slide)
def handleSlide(slide):
handleSlideTitle(slide.getElementsByTagName("title")[0])
handlePoints(slide.getElementsByTagName("point"))
def handleSlideshowTitle(title):
print(f"<title>{getText(title.childNodes)}</title>")
def handleSlideTitle(title):
print(f"<h2>{getText(title.childNodes)}</h2>")
def handlePoints(points):
print("<ul>")
for point in points:
handlePoint(point)
print("</ul>")
def handlePoint(point):
print(f"<li>{getText(point.childNodes)}</li>")
def handleToc(slides):
for slide in slides:
title = slide.getElementsByTagName("title")[0]
print(f"<p>{getText(title.childNodes)}</p>")
handleSlideshow(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:
Interfaces are accessed through instance objects. Applications should not
instantiate the classes themselves; they should use the creator functions
available on the Document object. Derived interfaces support all
operations (and attributes) from the base interfaces, plus any new operations.
Operations are used as methods. Since the DOM uses only in
parameters, the arguments are passed in normal order (from left to right).
There are no optional arguments. void operations return None.
IDL attributes map to instance attributes. For compatibility with the OMG IDL
language mapping for Python, an attribute foo can also be accessed through
accessor methods _get_foo() and _set_foo(). readonly
attributes must not be changed; this is not enforced at runtime.
The types short int, unsigned int, unsigned long long, and
boolean all map to Python integer objects.
The type DOMString maps to Python strings. xml.dom.minidom supports
either bytes or strings, but will normally produce strings.
Values of type DOMString may also be None where allowed to have the IDL
null value by the DOM specification from the W3C.
const declarations map to variables in their respective scope (e.g.
xml.dom.minidom.Node.PROCESSING_INSTRUCTION_NODE); they must not be changed.
DOMException is currently not supported in xml.dom.minidom.
Instead, xml.dom.minidom uses standard Python exceptions such as
TypeError and AttributeError.
NodeList objects are implemented using Python's built-in list type.
These objects provide the interface defined in the DOM specification, but with
earlier versions of Python they do not support the official API. They are,
however, much more "Pythonic" than the interface defined in the W3C
recommendations.
The following interfaces have no implementation in xml.dom.minidom:
DOMTimeStamp
EntityReference
Most of these reflect information in the XML document that is not of general utility to most DOM users.
註解