EVE Online begins moving 2.4 million lines to Python 3
CCP Games has shipped stage one to the live server after 16 years on Stackless Python 2.7, with 95.9 percent of files already compiling under both versions.
Illustration: a night-time data center aisle where cable bundles are being rerouted from older cabinets to newer racks.
On August 25, 2026, CCP Games deployed the first stage of EVE Online's move from Stackless Python 2.7 to Python 3 to the live Tranquility server, keeping the game on 2.7 while making its code compile under both interpreters.
At a glance
- Codebase: about 2.4 million lines of Python across roughly 20,000 files.
- 95.9 percent of files already compile under both Python 2.7 and Python 3.
- About 3,300 blocking lines remain, including ~1,500 print statements, 800 long literals, 600 old except clauses, 50 inequality operators.
- Roughly 20,000 lines compile under both versions but behave differently; stage 2 reviews them by hand.
- Tranquility has to stay reachable 23.75 of every 24 hours during the work.
EVE Online has run on Stackless Python since it launched in 2003, and on Stackless Python 2.7 since 2010. On August 25, 2026, CCP Games deployed the first stage of the long-deferred jump to Python 3 to Tranquility, the live server. The changes had been exercised on the Singularity test server in July.
Stage one does not switch interpreters
The goal of stage one is narrow and deliberately boring: make the code valid under Python 3 while it keeps running under Python 2.7. CCP is using the Python-Future tooling for the mechanical rewrites, so both interpreters accept the same files.
That framing matters. Nothing about the runtime changed for players this week — what changed is how much of the codebase is now portable.
The scale of the codebase
CCP puts the codebase at roughly 2.4 million lines of Python spread over about 20,000 files, each of which gets compiled under a real Python 2.7 interpreter. By the studio's count, 95.9 percent of those files already compile under both versions.
The remainder comes down to roughly 3,300 blocking lines. CCP breaks out about 1,500 legacy print statements, 800 long literals written as 123L, 600 deprecated except clauses, and 50 uses of the old inequality operator. All of that is the kind of syntax a migration script can rewrite.
Stage two is where humans are required
The harder pile is about 20,000 lines that compile cleanly under both versions and then do different things at runtime. Integer division is the canonical case: 1 / 2 evaluates to 0 under Python 2 and 0.5 under Python 3. No tool can tell which behavior the original author wanted, so each site needs a judgment call.
All of this happens against an availability constraint — the studio notes Tranquility has to keep running 23.75 hours out of every 24. There is no long maintenance window to hide the work in.
What the announcement leaves open
Writing about the post, Simon Willison points out that it does not explain how the Stackless-specific capabilities themselves get replaced. For EVE Frontier, the studio's newer title, CCP built the open-source carbonengine/scheduler library to fill that role in its Carbon engine — but whether EVE Online takes the same route is not stated, and this article does not assume it does.
CCP also gives no completion date. Stage one is described as done and stage two as next; there is no published schedule beyond that.
Why this case travels
The benefits CCP expects are the usual ones: performance gains from newer Python releases, access to current debugging and profiling tools, cleaner text and integer handling, and faster turnaround on features and bug fixes.
What makes the post worth reading outside the game's player base is the numbers. Twenty-plus years of Python at this scale rarely gets documented in public, and this one puts a price tag on deferring a runtime upgrade for 16 years. Details are in the CCP announcement.
FAQ
What is CCP Games actually changing in EVE Online's code?
Stage one rewrites Python 2-only syntax so the same files compile under both Python 2.7 and Python 3, using the Python-Future tooling. The game still runs on Stackless Python 2.7 for now; the interpreter switch has not happened yet.
Will the Python 3 migration cause more EVE Online downtime?
CCP announces no extra outages and stresses that Tranquility must stay reachable 23.75 out of every 24 hours. Stage one went to the live server after testing on Singularity in July.
When will EVE Online run fully on Python 3?
CCP has not given a date. The announcement describes stage one as deployed and stage two — the manual review of roughly 20,000 behaviorally different lines — as the next step, without a published timeline.
