python / python/cpython

Improve statistics.median() complexity

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performance stdlib type-feature
Dominant language
Python
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Forks
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Description

Median can be computed in time O(n log n) without sorting using the select-k algorithm.

https://github.com/python/cpython/blob/169cdfefce83fabcea48d0ba24ca4dba210f41d0/Lib/statistics.py#L327C1-L348C43

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Read the median implementation in Lib/statistics.py at the linked lines and determine how its current sorting step can be replaced by a select-k approach. Check that the resulting implementation preserves median behavior while avoiding a full sort, and verify the complexity improvement with the relevant statistics tests.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
performance
Issue type
Refactor
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
45/100

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