insertion_sort.py

"""
This is a pure python implementation of the insertion sort algorithm

For doctests run following command:
python -m doctest -v insertion_sort.py
or
python3 -m doctest -v insertion_sort.py

For manual testing run:
python insertion_sort.py
"""
from __future__ import print_function


def insertion_sort(collection):
    """Pure implementation of the insertion sort algorithm in Python

    :param collection: some mutable ordered collection with heterogeneous
    comparable items inside
    :return: the same collection ordered by ascending

    Examples:
    >>> insertion_sort([0, 5, 3, 2, 2])
    [0, 2, 2, 3, 5]

    >>> insertion_sort([])
    []

    >>> insertion_sort([-2, -5, -45])
    [-45, -5, -2]
    """
    for index in range(1, len(collection)):
        while 0 < index and collection[index] < collection[index - 1]:
            collection[index], collection[
                index - 1] = collection[index - 1], collection[index]
            index -= 1

    return collection


if __name__ == '__main__':
    import sys

    # For python 2.x and 3.x compatibility: 3.x has no raw_input builtin
    # otherwise 2.x's input builtin function is too "smart"
    if sys.version_info.major < 3:
        input_function = raw_input
    else:
        input_function = input

    user_input = input_function('Enter numbers separated by a comma:\n')
    unsorted = [int(item) for item in user_input.split(',')]
    print(insertion_sort(unsorted))