I have implemented a Bubble Sort. It works well. But if you think something needs to be improved, say it. This code was tested in Python 3.7.4.

def bubble_sort(nums):

    for i in range(len(nums)-1):
        for j in range(0,len(nums)-1-i,1):
            if nums[j] > nums[j+1]:
                swap(nums, j, j+1)

    return nums

def swap(nums, i, j):
    temp = nums[i]
    nums[i] = nums[j]
    nums[j] = temp

if __name__ == "__main__":

   a = [0,0,0,-1,-0,1,2,3,2,1]

2 Answers 2


Unnecessary Function

Your swap function is unnecessary. Simply replace the function call with this line:

nums[j], nums[j + 1] = nums[j + 1], nums[j]

This does the swapping for you.


There should be spaces between values in lists

[1, 2, 3, 4, 5]

between numbers/strings and operators

if nums[j] > nums[j + 1]

and between parameters in a function call

for j in range(0, len(nums) - 1 - i, 1):

Type Hints

Your function header can look like this:

from typing import List, Union

def bubble_sort(nums: List[Union[int, float]]) -> List[Union[int, float]]:

What this says is that the function accepts a list of integers/floats, and returns a list of integers/floats. It adds another layer of descriptiveness to your code.


You should include a docstring at the beginning of every class/method/module you write. This allows you to describe in words what your code is doing.

def bubble_sort(nums: List[Union[int, float]]) -> List[Union[int, float]]:
    A bubble sort algorithm, etc etc etc

    :param nums -> List: A list of integers/floats to sort

    :return List: The sorted list of integers/floats, from smallest -> biggest

In addition to Linny's answer, one can also optimize the bubble sort algorithm like this:

def bubble_sort(nums):  # sorry that I am too lazy to include type hints here :)
    for i in range(len(nums) - 1):
        found = False
        for j in range(len(nums) - 1 - i):  # start == 0 and step == 1 are unnecessary
            if nums[j] > nums[j + 1]:
                nums[j], nums[j + 1] = nums[j + 1], nums[j]
                found = True  # it means that there is at least a swap
        if not found:  # if there is no swap it means that there is no need to go for next value of i

    return nums

Hope it helps.


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