Insertion Sort Algorithm in Python

Implementing basic sorting algorithms to learn them, and coding, better. Criticisms/ critiques welcome. Also possible optimizations.

import unittest
import random

def insertion_sort(seq):
    """Accepts a mutable sequence, utilizes insertion sort algorithm to sort in
    place. Returns an ordered list"""
    #marks point between ordered sublist & unordered list
    partition = 1

    while partition < len(seq):
        temp = partition

        #while temp not in correct pos in sublist, decrement pos
        while temp != 0 and seq[temp] < seq[temp-1]:
            seq[temp], seq[temp-1] = seq[temp-1], seq[temp]
            temp -= 1

        partition += 1

    return seq

class test_insertionsort(unittest.TestCase):
    def test_insertionsort(self):
        """Test insertion_sort()"""
        seq = [random.randrange(0, 1000) for _ in range(1000)]
        self.assertEqual(insertion_sort(seq), sorted(seq))

if __name__ == '__main__':
    unittest.main()

One thing that can speed up insertion sort is to pull the partition value to the side and slide elements up into the vacancy until the correct location is found, then drop the partition value into that location. This eliminates one of the three assignments in the while loop:

for p in range(1, len(seq)):
    if seq[p] >= seq[p-1]:
        continue
    p_value = seq[p]
    while p != 0 and p_value < seq[p-1]:
        seq[p] = seq[p-1]
        p -= 1
    seq[p] = p_value
return seq

The unit test shows a substantial speed improvement from doing this.

StackExchange Code Review Q#40809, answer score: 3