Source Code for Module concurrent_tree_crawler.abstract_tree_navigator

 1 -class NavigationException(Exception): 
 2          """ 
 3          See the description of C{AbstractTreeNavigator} class for a discussion 
 4          on the usage of this exception. 
 5          """              
 6          pass 
 7   
 8 -class AbstractTreeNavigator: 
 9          """ 
10          An object that has a direct access to the elements of the domain tree  
11          (e.g. web pages) traversed by the crawler. 
12           
13          Each method declared in this abstract class can raise a  
14          L{NavigationException}. If such an exception is raised, it will be gently 
15          handled by the crawler -- it won't terminate the crawler thread nor 
16          the whole program, but the information that an error occurred will be saved 
17          in the tree data structure and the crawler will be restarted. If other 
18          kind of exception is raised, it will terminate the thread and the whole  
19          program. 
20          """ 
21           
22 -        def start_in_root(self): 
23                  """ 
24                  Start in the root node of the domain tree 
25                   
26                  @raise NavigationException: see class description for details of 
27                          ramification of raising such an exception. 
28                  """ 
29                  return NotImplementedError 
30   
31 -        def get_children(self): 
32                  """ 
33                  @return: names of children of the current node of the domain tree 
34                  @rtype: list of strings 
35                   
36                  @raise NavigationException: see class description for details of 
37                          ramification of raising such an exception. 
38                  """ 
39                  return NotImplementedError 
40   
41 -        def move_to_child(self, child_name): 
42                  """ 
43                  Move to the child of the current node of the domain tree. 
44                   
45                  @param child_name: name of the child to move to          
46                  @raise NavigationException: see class description for details of 
47                          ramification of raising such an exception. 
48                  """ 
49                  return NotImplementedError 
50                   
51 -        def move_to_parent(self): 
52                  """ 
53                  Move to the parent of the current node of the domain tree. 
54                   
55                  @raise NavigationException: see class description for details of 
56                          ramification of raising such an exception. 
57                  """ 
58                  return NotImplementedError 
59   
60 -        def process_node_and_check_if_is_leaf(self): 
61                  """ 
62                  @return: C{True} if the current node is a leaf, C{False} if it is  
63                          an internal node of the domain tree. 
64                  @raise NavigationException: see class description for details of 
65                          ramification of raising such an exception. 
66                  """ 
67                  return NotImplementedError 
68