multidict

multidict is a mapping implementation that allows multiple values per key, mirroring the semantics of HTTP headers and query strings. It provides four concrete classes — MultiDict (mutable), MultiDictProxy (immutable view), CIMultiDict (case-insensitive mutable), and CIMultiDictProxy (case-insensitive immutable view) — plus the istr helper for pre-folded string keys. Current version is 6.7.1 (released January 2026). The library ships an optional C extension; release cadence is frequent patch releases with periodic minor releases adding features such as the new merge() method (6.6.0) and a hash-table backend replacing the previous O(N) array (6.5.0).