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Space-efficient Bloom filter in Python
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| """ | |
| EXAMPLE | |
| >> bloom = Bloom(1000000, 6) # Instantiate a Bloom filter of size 100,000 with 6 runs through the hash function | |
| >> [bloom.insert(str(x)) for x in range(10000)] # Insert the integers from 0-9999 into the Bloom Filter | |
| >> all([bloom.lookup(str(x)) for x in range(10000)]) # Ensure all values were entered correctly | |
| True | |
| """ | |
| from bitarray import bitarray | |
| import mmh3 | |
| class Bloom(object): | |
| def __init__(self, size, hash_count, hash_f=mmh3.hash): | |
| self.size = size | |
| self.hash_count = hash_count | |
| self.hash_f = hash_f | |
| self.ba = bitarray(size) | |
| self.ba.setall(0) | |
| def insert(self, value): | |
| for seed in range(self.hash_count): | |
| hashed = self.hash_f(value, seed) % self.size | |
| self.ba[hashed] = 1 | |
| def lookup(self, value): | |
| for seed in range(self.hash_count): | |
| hashed = self.hash_f(value, seed) % self.size | |
| if not self.ba[hashed]: | |
| return False | |
| return True |
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