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本文實例講述了Python通過正則表達式選取callback的方法。分享給大家供大家參考。具體如下：

最近在瞎想怎么通過xpath去精確抓取文章的正文，跟parselets類似的想法，只不過更簡單。

代碼設計上采用正則表達式匹配URL，再選擇callback handler的方式，主要參考web.py的分發器（Dispatcher)。

當然，這個實現比較老土一些，全部用function的方式回調，沒有用類。

				?

									#!/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.';