Basic sorting in Python

Previously asked here.

I would like to get my code for implementation of simple sorting algorithms in idiomatic python code reviewed. I am looking for feedback on python idioms used, better ways of doing the same thing. I am familiar with FP, and I am willing to put in effort to get myself familiar with pythonic idioms such as list comprehensions and enumerators. Hence I would also like feedback on if any of the explicit loops can be converted to these.

import doctest
from hypothesis import given
import hypothesis.strategies as st

Insertion Sort

def insertionsort(items):
    """
    >>> insertionsort([])
    []
    >>> insertionsort([1])
    [1]
    >>> insertionsort([1,2,3,4,5])
    [1, 2, 3, 4, 5]
    >>> insertionsort([4,5,3,1,2])
    [1, 2, 3, 4, 5]
    """
    for k, v in enumerate(items):
        for i, val in enumerate(items[:k]):
            if v < val:
                items[i], items[i + 1:k + 1] = items[k], items[i:k]
                break
    return items

@given(st.lists(elements=st.integers()))
def test_insertionsort(x):
    assert insertionsort(x) == sorted(x)

Selection Sort

def selectionsort(items):
    """
    >>> selectionsort([])
    []
    >>> selectionsort([1])
    [1]
    >>> selectionsort([1, 0])
    [0, 1]
    >>> selectionsort([2, 1, 0])
    [0, 1, 2]
    >>> selectionsort([1,2,3,4,5])
    [1, 2, 3, 4, 5]
    >>> selectionsort([4,5,3,1,2])
    [1, 2, 3, 4, 5]
    """
    for k in reversed(range(1, len(items))):
        v, i = max((v, i) for i, v in enumerate(items[:k]))
        if items[k] < v:
            items[k], items[i] = items[i], items[k]
    return items

@given(st.lists(elements=st.integers()))
def test_selectionsort(x):
    assert selectionsort(x) == sorted(x)

Bubble Sort

```
def bubblesort(items):
"""
>>> bubblesort([])
[]
>>> bubblesort([1])
[1]
>>> bubblesort([1, 0])
[0, 1]
>>> bubblesort([2, 1, 0])
[0, 1, 2]
>>> bubblesort([1,2,3,4,5])
[1, 2, 3, 4, 5]

Your code looks nice and well tested: congratulations. I have a few comments anyway.

A little design/API comment

Compare sorted:


sorted(iterable[, key][, reverse])


Return a new sorted list from the items in iterable.

and list.sort:


sort(*, key=None, reverse=None)


This method sorts the list in place[...] it does not return the sorted sequence.

The difference is that one operates in place and the other one returns a new list. Your code does both which is likely to be confusing.

Other various comments

You could (and probably should) pass the sorting function as a parameter to your testing function. You'd have something like :

@given(st.lists(elements=st.integers()))
def test_sort(x, my_sorted):
    assert my_sorted(x) == sorted(x)

and :

for s in [selection, bubble, insertion, quicksort, mergesort, heapsort, shellsort]:
    test_sort(s)

The variable name mod might a bit confusing as one might think about the modulo operator. I guess modif or change would be better.

Suggestion

It might be worth defining a swap(i, j) function/method but it might affect performances.

StackExchange Code Review Q#123318, answer score: 2