本文实例讲述了Python通过正则表达式选取callback的方法。分享给大家供大家参考。具体如下：

最近在瞎想怎么通过xpath去精确抓取文章的正文，跟parselets类似的想法，只不过更简单。

代码设计上采用正则表达式匹配URL，再选择callback handler的方式，主要参考web.py的分发器（Dispatcher)。

当然，这个实现比较老土一些，全部用function的方式回调，没有用类。

#!/bin/env python
import re, sys
# Define parser first.
def baidu(username):
  # Business logic
  return \"Using parser Baidu. and the user\'s name is: %s.\" % username
def qzone(uin):
  # Business logic
  return \"Using parser Qzone, and the user\'s QQ is: %s.\" % uin
# From web.py
def group(seq, size):#{{{
  \"\"\"
  Returns an iterator over a series of lists of length size from iterable.
    >>> list(group([1,2,3,4], 2))
    [[1, 2], [3, 4]]
    >>> list(group([1,2,3,4,5], 2))
    [[1, 2], [3, 4], [5]]
  \"\"\"
  def take(seq, n):
    for i in xrange(n):
      yield seq.next()
  if not hasattr(seq, \'next\'):
    seq = iter(seq)
  while True:
    x = list(take(seq, size))
    if x:
      yield x
    else:
      break
#}}}
def parser_init(url,mapping):
  for pat, what in group(mapping,2):
    result = re.compile(\'^\' + pat + \'$\').match(url)
    if result:
      return what, [x for x in result.groups()]
  return None, None
if __name__ == \'__main__\':
  mapping = (
      \'http://(?:hi|space).baidu.com/([^/]+)(?:/.*)?\',\'baidu\',
      \'http://(\\d+).qzone.qq.com(?:/.*)?\',\'qzone\',
      )
  (func, args) = parser_init(sys.argv[1],mapping)
  if func:
    callback = func
    if func in globals():
      callback = globals()[func]
    if callable(callback):
      print callback(*args)
  else:
    print \'No parser found.\';

希望本文所述对大家的Python程序设计有所帮助。