xml.dom.pulldom
— 支持构建部分 DOM (文档对象模型) 树
¶
xml.dom.pulldom
module provides a “pull parser” which can also be asked to produce DOM-accessible fragments of the document where necessary. The basic concept involves pulling “events” from a stream of incoming XML and processing them. In contrast to SAX which also employs an event-driven processing model together with callbacks, the user of a pull parser is responsible for explicitly pulling events from the stream, looping over those events until either processing is finished or an error condition occurs.
警告
xml.dom.pulldom
module is not secure against maliciously constructed data. If you need to parse untrusted or unauthenticated data see
XML vulnerabilities
.
Changed in version 3.6.7: The SAX parser no longer processes general external entities by default to increase security by default. To enable processing of external entities, pass a custom parser instance in:
from xml.dom.pulldom import parse
from xml.sax import make_parser
from xml.sax.handler import feature_external_ges
parser = make_parser()
parser.setFeature(feature_external_ges, True)
parse(filename, parser=parser)
范例：
from xml.dom import pulldom
doc = pulldom.parse('sales_items.xml')
for event, node in doc:
if event == pulldom.START_ELEMENT and node.tagName == 'item':
if int(node.getAttribute('price')) > 50:
doc.expandNode(node)
print(node.toxml())
event
is a constant and can be one of:
START_ELEMENT
END_ELEMENT
COMMENT
START_DOCUMENT
END_DOCUMENT
CHARACTERS
PROCESSING_INSTRUCTION
IGNORABLE_WHITESPACE
node
is an object of type
xml.dom.minidom.Document
,
xml.dom.minidom.Element
or
xml.dom.minidom.Text
.
Since the document is treated as a “flat” stream of events, the document “tree” is implicitly traversed and the desired elements are found regardless of their depth in the tree. In other words, one does not need to consider hierarchical issues such as recursive searching of the document nodes, although if the context of elements were important, one would either need to maintain some context-related state (i.e. remembering where one is in the document at any given point) or to make use of the
DOMEventStream.expandNode()
method and switch to DOM-related processing.
xml.dom.pulldom.
PullDom
(
documentFactory=None
)
¶
Subclass of
xml.sax.handler.ContentHandler
.
xml.dom.pulldom.
SAX2DOM
(
documentFactory=None
)
¶
Subclass of
xml.sax.handler.ContentHandler
.
xml.dom.pulldom.
parse
(
stream_or_string
,
parser=None
,
bufsize=None
)
¶
返回
DOMEventStream
from the given input.
stream_or_string
may be either a file name, or a file-like object.
parser
, if given, must be an
XMLReader
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:
xml.dom.pulldom.
parseString
(
string
,
parser=None
)
¶
返回
DOMEventStream
that represents the (Unicode)
string
.
xml.dom.pulldom.
default_bufsize
¶
Default value for the
bufsize
parameter to
parse()
.
The value of this variable can be changed before calling
parse()
and the new value will take effect.
xml.dom.pulldom.
DOMEventStream
(
stream
,
parser
,
bufsize
)
¶
getEvent
(
)
¶
Return a tuple containing
event
和当前
node
as
xml.dom.minidom.Document
if event equals
START_DOCUMENT
,
xml.dom.minidom.Element
if event equals
START_ELEMENT
or
END_ELEMENT
or
xml.dom.minidom.Text
if event equals
CHARACTERS
. The current node does not contain information about its children, unless
expandNode()
被调用。
expandNode
(
node
)
¶
Expands all children of node into node 。范例：
from xml.dom import pulldom
xml = '<html><title>Foo</title> <p>Some text <div>and more</div></p> </html>'
doc = pulldom.parseString(xml)
for event, node in doc:
if event == pulldom.START_ELEMENT and node.tagName == 'p':
# Following statement only prints '<p/>'
print(node.toxml())
doc.expandNode(node)
# Following statement prints node with all its children '<p>Some text <div>and more</div></p>'
print(node.toxml())
reset
(
)
¶