Created
January 1, 2019 02:28
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MonotonicExpandingSequence
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# A bit of cleverness to create a new sequence for infinite iterators | |
from collections.abc import Sequence | |
class MonotonicExpandingSequence(Sequence): | |
def __init__(self, iterator): | |
self.iterator = iterator | |
self._cache = [] | |
def __getitem__(self, index): | |
while len(self._cache) <= index: | |
self._cache.append(next(self.iterator)) | |
return self._cache[index] | |
def __len__(self): | |
return len(self._cache) | |
def __contains__(self, num): | |
i = 0 | |
while True: | |
if self[i] == num: | |
return True | |
elif self[i] > num: | |
return False | |
else: | |
i += 1 | |
# Usage, e.g.: | |
# primes = MonotonicExpandingSequence(get_all_primes()) | |
# if 257 in primes: ... | |
# if 258 in primes: ... | |
# n = primes[100] |
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