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UID:pretalx-europython-2026-GEJAQW@programme.europython.eu
DTSTART;TZID=CET:20260716T120500
DTEND;TZID=CET:20260716T123500
DESCRIPTION:Python supports parallelism through multiple sub-interpreters. 
 Parallelism though sub-interpreters avoid the restrictions of a single GIL
 \, and isolating parallel processes from each other is safe from data-race
 s. The downside is that subinterpreter isolation comes with a high cost: s
 ending objects across sub-interpreters typically involves pickling and cop
 ying which has negative impact on performance with both CPU and memory ove
 rheads. This talk is about [PEP795](https://pep-previews--4468.org.readthe
 docs.build/pep-0795/) which adds immutability to Python\, which permits su
 b-interpreters to transfer and share immutable objects directly by referen
 ce. \n\nWe will present the design and rationale for immutability in Pytho
 n\, the API for creating and managing immutable state\, decorators for com
 municating immutability in code\, as well as opting out of immutability wh
 ere necessary. We will also discuss our prototype implementation on-top of
  Python 3.15\, and demonstrate how immutable sharing across sub-interprete
 rs improves performance\, and compare the speed of freezing (the act of ma
 king objects immutable) to pickling and unpickling. \n\nAttendees will lea
 rn:\n\n* About the semantics of immutability in Python\, and what are the 
 challenges of designing immutability to support sharing across sub-interpr
 eters.\n* When immutability can improve performance and predictability in 
 concurrent Python.\n* How freezing works for built-in types\, user‑defin
 ed types and functions\, and how it interacts with sub-interpreters.\n* Pe
 rformance of pickling vs. immutable sharing\, with numbers and failure mod
 es.\n* Current limitations of immutability\, risks\, and what would need t
 o land in CPython for this to be widely usable. Target audience: programme
 rs interested in concurrent programming in Python.\n    \n\nNote: This PEP
  is not yet accepted\; the talk focuses on design\, prototype results\, an
 d open questions.
DTSTAMP:20260524T122014Z
LOCATION:Auditorium Hall (S1)
SUMMARY:Immutability: Fast and Safe sharing of Data across Subinterpreters 
 - Fridtjof Stoldt\, Tobias Wrigstad
URL:https://programme.europython.eu/europython-2026/talk/GEJAQW/
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