bloom-filter

Note: This project has gone unmaintained for a while, please use the more up-to-date project at:

• https://github.com/remram44/python-bloom-filter
• https://pypi.org/project/bloom-filter2/

A pure python bloom filter (low storage requirement, probabilistic set datastructure) is provided. It is known to work on CPython 2.x, CPython 3.x, Pypy and Jython.

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

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

Usage:

::

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" in bloom is False

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

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