bottle.py中的路由搜索优化

# Now search regexp routes
# ROUTES_REGEXP是一个字典，键是请求方法，值是[路由, 处理函数]的列表
# 例如：{"GET", [[路由1, 处理函数1], [路由2, 处理函数2]]}
routes = ROUTES_REGEXP.get(method,[])
for i in xrange(len(routes)):
    match = routes[i][0].match(url)
    if match:
        handler = routes[i][1]
        if i > 0 and OPTIMIZER and random.random() <= 0.001:
          # Every 1000 requests, we swap the matching route with its predecessor.
          # Frequently used routes will slowly wander up the list.
          # 有千分之一的概率，可以与前面的路由互换位置，这样使用越频繁的路由就会
          # 被换的越靠前，搜索起来效率就越高
          routes[i-1], routes[i] = routes[i], routes[i-1]
        return handler, match.groupdict()
raise HTTPError(404, "Not found")