1from __future__ import absolute_import, division, unicode_literals
2
3try:
4 from collections.abc import Mapping
5except ImportError: # Python 2.7
6 from collections import Mapping
7
8
9class Trie(Mapping):
10 """Abstract base class for tries"""
11
12 def keys(self, prefix=None):
13 # pylint:disable=arguments-differ
14 keys = super(Trie, self).keys()
15
16 if prefix is None:
17 return set(keys)
18
19 return {x for x in keys if x.startswith(prefix)}
20
21 def has_keys_with_prefix(self, prefix):
22 for key in self.keys():
23 if key.startswith(prefix):
24 return True
25
26 return False
27
28 def longest_prefix(self, prefix):
29 if prefix in self:
30 return prefix
31
32 for i in range(1, len(prefix) + 1):
33 if prefix[:-i] in self:
34 return prefix[:-i]
35
36 raise KeyError(prefix)
37
38 def longest_prefix_item(self, prefix):
39 lprefix = self.longest_prefix(prefix)
40 return (lprefix, self[lprefix])