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from __future__ import absolute_import, division, unicode_literals
from collections import Mapping
class Trie(Mapping):
"""Abstract base class for tries"""
def keys(self, prefix=None):
keys = super().keys()
if prefix is None:
return set(keys)
# Python 2.6: no set comprehensions
return set([x for x in keys if x.startswith(prefix)])
def has_keys_with_prefix(self, prefix):
for key in self.keys():
if key.startswith(prefix):
return True
return False
def longest_prefix(self, prefix):
if prefix in self:
return prefix
for i in range(1, len(prefix) + 1):
if prefix[:-i] in self:
return prefix[:-i]
raise KeyError(prefix)
def longest_prefix_item(self, prefix):
lprefix = self.longest_prefix(prefix)
return (lprefix, self[lprefix])
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