Simon Willison’s Weblog

Bloom Filters, explained by Sam Rose. Beautifully designed explanation of bloom filters, complete with interactive demos that illustrate exactly how they work.

# 23rd February 2024, 3:59 pm / bloom-filters, explorables, sam-rose

How CPython Implements and Uses Bloom Filters for String Processing. Fascinating dive into Python string internals by Abhinav Upadhyay. It turns out CPython uses very simple bloom filters in several parts of the core string methods, to solve problems like splitting on newlines where there are actually eight codepoints that could represent a newline, and a tiny bloom filter can help filter a character in a single operation before performing all eight comparisons only if that first check failed.

# 16th September 2023, 10:32 pm / bloom-filters, performance, python

All you ever wanted to know about writing bloom filters. This helped me understand a key use case for bloom filters: reducing the impact of the “worst case search is when there are no matching results so everything gets scanned” problem.

# 30th January 2009, 8:26 am / bloom-filters, jonathan-ellis, search

Bloom Filter Resources. A continuation of the discussion about how to transfer information about a large number of recently updated resources around in an efficient way, Joe provides working code illustrating a simple approach using bloom filters.

# 19th October 2008, 10:22 pm / bloom-filters, hashing, joe-gregorio, rest