bloom-filter

A pure python bloom filter (low storage requirement, probabilistic set datastructure) is provided. It is known to work on CPython 3.x, Pypy, and Jython.

Includes mmap, in-memory and disk-seek backends.

This project builds on drs-bloom-filter and bloom_filter_mod. Credits and links can be found in AUTHORS.md.

Usage

The user specifies the desired maximum number of elements and the desired maximum false positive probability, and the module calculates the rest.

from bloom_filter import BloomFilter

# instantiate BloomFilter with custom settings,
# max_elements is how many elements you expect the filter to hold.
# error_rate defines accuracy; You can use defaults with
# `BloomFilter()` without any arguments. Following example
# is same as defaults:
bloom = BloomFilter(max_elements=10000, error_rate=0.1)

# Test whether the bloom-filter has seen a key:
assert "test-key" not in bloom

# Mark the key as seen
bloom.add("test-key")

# Now check again
assert "test-key" in bloom