PyRanking

Strategies to assign ranks

Strategies to assign ranks

In most cases, a sorting function is a best tool to make a ranking. But how about tie scores? You may end up with giving different ranks for tie scores. And I'm quite sure that will make your users dissatisfied.

Solution? You are on the right page.

This module provides various ranking strategies to assign correct ranks to tie scores. It comes with 5 most common strategies: competition, modified-competition, dense, ordinal, and fractional.

Installation

python -m pip install pyranking

Usage

Suppose we want to rank an array of computer languages by the year they were introduced.

languages = [
  { "name": 'Javascript', "year": 1995 },
  { "name": 'Java', "year": 1995 },
  { "name": 'C#', "year": 2001 },
  { "name": 'Groovy', "year": 2003 },
  { "name": 'Scala', "year": 2003 },
  { "name": 'Go', "year": 2009 },
];

We need to provide a function defining the sorting criteria. The function must accept one entry of the array and returns a value to rank on (the year in this case). Note the returned value can be directly an attribute of the object, or any computed value based on that object (e.g. the math test score plus the English test score of a student).

score_fn = lambda x: x["year"]

Let's run the ranking operation on this list of languages

from pyranking import rank
ranked_languages = rank(languages, score_fn);

The ranked_languages is an array that looks like below. By default, it sorts by descending order, using the competition strategy, and starts ranking at 1

[ { "rank": 1, "item": { "name": 'Go', "year": 2009 } },
  { "rank": 2, "item": { "name": 'Groovy', "year": 2003 } },
  { "rank": 2, "item": { "name": 'Scala', "year": 2003 } },
  { "rank": 4, "item": { "name": 'C#', "year": 2001 } },
  { "rank": 5, "item": { "name": 'Javascript', "year": 1995 } },
  { "rank": 5, "item": { "name": 'Java', "year": 1995 } } ]

To change the ranking strategy, use the optional parameter strategy.

const ranked_anguages = rank(languages, score_fn, strategy="dense");

To sort in ascending order

const ranked_languages = rank(languages, score_fn, reverse=True);

To start ranking at any number (e.g. 5).

const ranked_anguages = rank(languages, score_fn, start=5);
// Go language would have a rank of 5.

License

MIT