Python Regex：这有什么问题？

Question

I am trying to do a regex to just get the error code from this XML.

>>> re_code = re.compile(r'<errorcode>([0-9]+)</errorcode>', re.MULTILINE)
>>> re_code.match('''<?xml version="1.0" encoding="ISO-8859-1" standalone="no"?>
... <methoderesponse>
...     <status>
...         <message/>
...         <errorcode>515</errorcode>
...         <value>ERROR</value>
...     </status>
... </methoderesponse>
... ''')

It should be quite easy. But I don't understand why it doesn't match.

Answer 1

.match() attempts to match at the start. You want .search() or more likely .findall()

Have a look at an XML parser though - much nicer to use XPath or equivalent to get your data (plus it'll handle nuances that regex's won't)

An example that works with your sample XML:

import xml.etree.ElementTree as ET
tree = ET.fromstring(text)

>>> tree.findall('.//errorcode')[0].text
'515'

More info about ElementTree here and I would personally check out lxml

Answer 2

as @ Jon Clements has said, .match() only works if the expression is supposed to run from the beginning of the string, .search() searches the string for the first occurrence, and .findall() searches for all the occurrences.

but regardless of that, you should modify slightly your regular expression to a slightly more readable version:

regex = re.compile(r'<errorcode>(\d+)</errorcode>')

you don't need the re.MULTILINE argument, it does not pertain to this problem.