Python uses expat to parse XML

Python has some built-in XML parsing libraries. This article introduces the expat library in Python.

Expat supports dynamic parsing of XML. What is dynamic? That is, an XML string does not need to be completely input to expat. Even if it is only a part, expat can also sense the RESPONSE event. Event? For example, if a new element is detected (in essence, expat encounters '<'), or an element is detected to have been processed ('/> '). So -- expat does not necessarily need complete XML to work.

ViewProgram

 1   Import  XML. parsers. Expat  2   3   Class  Exparser (object ):  4       ''' Parse roster XML  '''  5       Def   _ Init __  (Self, xml_raw ):  6           '''  Init parser and setup handlers  '''  7 Self. parser = XML. parsers. Expat. parsercreate ()  8   9           #  Connect handlers 10 Self. parser. startelementhandler = Self. start_element  11 Self. parser. endelementhandler = Self. end_element  12 Self. parser. characterdatahandler = Self. char_data  13   Self. parser. parse (xml_raw)  14           Del  (Xml_raw)  15   16       Def Start_element (self, name, attrs ):  17           '''  Start XML Element Handler  '''  18           Print  'Start: '+ name  19   20       Def  End_element (self, name ):  21           '''  End XML Element Handler  ''' 22           Print  'End: '+ name  23   24       Def  Char_data (self, data ):  25           '''  Char XML Element Handler  '''  26           Print 'Data is '+ Data

Ah analysis:

An expat parser is defined in the construction of the 7-row exparser.

Line 10-12 sets the callback function of interest for the parser

Line 13 begins parsing our XML

The next step is to wait for expat resolution. Once the expat parser encounters an XML element, the element ends. When the element value event occurs, the start_element, end_element, and char_data functions will be called separately.

The 16-line parameter name, attrs representing the node name, node attribute (dictionary)

Line 20 parameter name indicates the node name

24-line parameter data indicates node data

After getting these values, you can do anything.

In particular, when we encounter large XML data blocks, we can use expat to dynamically parse this point to parse a large block.