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A pure Python skiplist.

Project description

A pure Python skiplist implementation.

A skiplist provides a quickly searchable structure (like a balanced binary tree) that also updates fairly cheaply (no nasty rebalancing acts). In other words, it’s awesome.

See for more information.

Written mostly an exercise for myself, it turns out skiplists are really useful. It also comes with a (mostly-underdocumented) linked-list implementation (+ a sorted variant), if that’s useful.


  • Python 3.3+ (should work on Python 2.6+ as well, as well as PyPy 2.0+)
  • nose>=1.30 for running unittests


Using it looks like:

>>> import skiplist
>>> skip = skiplist.Skiplist()
>>> len(skip)
>>> 6 in skip
>>> skip.insert(0)
>>> skip.insert(7)
>>> skip.insert(3)
>>> skip.insert(6)
>>> skip.insert(245)
>>> len(skip)
>>> 6 in skip
>>> skip.remove(245)
>>> len(skip)
>>> skip.find(3)
<Skiplist: 3>


Performance is alright, though I’m sure there’s room for improvement. See the script for more information.

Running Tests

Run pip install nose (preferrably within a virtualenv) to install nose.

Then run nosetests -s -v to exercise the full suite.


  • A more performant implementation of remove (still O(N))

  • More performance testing

    • Loading data seems slow


author:Daniel Lindsley

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