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57 lines
1.7 KiB
Python
57 lines
1.7 KiB
Python
# Copyright 2012 Google Inc. All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""
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Iterator wrapper that allows you to check whether the wrapped iterator
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is empty and whether it has more than 1 element.
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"""
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class PluralityCheckableIterator(object):
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def __init__(self, it):
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self.it = it.__iter__()
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self.head = []
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# Populate first 2 elems into head so we can check whether iterator has
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# more than 1 item.
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for i in range(0, 2):
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self.__populate_head__()
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def __populate_head__(self):
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try:
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e = self.it.next()
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self.underlying_iter_empty = False
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self.head.append(e)
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except StopIteration:
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# Indicates we can no longer call next() on underlying iterator, but
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# there could still be elements left to iterate in head.
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self.underlying_iter_empty = True
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def __iter__(self):
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while len(self.head) > 0:
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yield self.next()
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else:
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raise StopIteration()
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def next(self):
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# Backfill into head each time we pop an element so we can always check
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# for emptiness and for has_plurality().
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self.__populate_head__()
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return self.head.pop(0)
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def is_empty(self):
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return len(self.head) == 0
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def has_plurality(self):
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return len(self.head) > 1
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