My implementation of bubble sort using Python

Question

I just started studying algorithms and since I'm most familiar with Python decided to use it to actually put the algorithms I've been learning to use. How is my implementation of Bubble Sort? Does it make sense, is it efficient, too many variables, can you understand it without comments, any other tips for me?

"""
Bubble sort algorithm.
"""
import random
ls = []
max_length = 10
while len(ls) < max_length:
    ls.append(random.randint(1,101))
print ls
def bubble_sort(items_to_sort):
    right_item = -1 
    left_item = -2
    item_len = len(items_to_sort)
    number_of_passes = 0
    temp_item = 0
    max_checks = len(items_to_sort)
    if item_len > 1:
        while (number_of_passes < item_len) and (max_checks > 0):
            if items_to_sort[right_item] < items_to_sort[left_item]:
                temp_item = items_to_sort[right_item]  
                items_to_sort[right_item] = items_to_sort[left_item] 
                items_to_sort[left_item] = temp_item 
            right_item += -1
            left_item += -1
            number_of_passes += 1
            if left_item < -(item_len):
                right_item = -1
                left_item = -2
                number_of_passes = 0
                max_checks -= 1
    return items_to_sort    
print bubble_sort(ls)

Answer 1

Your bubble sort algorithm has way too many variables. You don't need to keep track of the right and left item. All you need to do is compare two values, and swap if one is bigger than the other.

def bubble_sort(nums):
    length = len(nums)
    for i in range(length - 1):
        for j in range(0, length - i - 1):
            if nums[j] > nums[j + 1]:
                nums[j], nums[j + 1] = nums[j + 1], nums[j]

After benchmarking, this code is substantially faster than your original code.

Benchmarks:

Array size bubble_sort_op       3000    1.87206s
Array size bubble_sort          3000    0.67218s
Array size bubble_sort_op       3200    2.24581s
Array size bubble_sort          3200    0.78276s
Array size bubble_sort_op       3400    2.41464s
Array size bubble_sort          3400    0.87018s
Array size bubble_sort_op       3600    2.69006s
Array size bubble_sort          3600    0.96319s
Array size bubble_sort_op       3800    2.99190s
Array size bubble_sort          3800    1.09713s
Array size bubble_sort_op       4000    3.48652s
Array size bubble_sort          4000    1.24830s