{"id":19149,"date":"2020-12-03T04:15:16","date_gmt":"2020-12-03T12:15:16","guid":{"rendered":"https:\/\/careerkarma.com\/blog\/?p=19149"},"modified":"2023-12-01T04:05:34","modified_gmt":"2023-12-01T12:05:34","slug":"python-bubble-sort-a-how-to-guide","status":"publish","type":"post","link":"https:\/\/careerkarma.com\/blog\/python-bubble-sort-a-how-to-guide\/","title":{"rendered":"Python Bubble Sort: A How-To Guide"},"content":{"rendered":"\n

A Python bubble sort goes through a list and compares elements next to each other. If an element on the right is greater than one on the left, the elements are swapped. This happens until the list is sorted.<\/em><\/p>\n\n\n\n

Do you need to sort a list? The bubble sort has got your back. The bubble sort is a type of standard algorithm that sorts lists. It is perhaps the simplest sort out there, so it\u2019s perfect for beginners who are new to sorting algorithms!\n\n<\/p>\n\n\n\n

In this guide, we\u2019re going to discuss how bubble sorts work and how you can implement a Python bubble sort algorithm. We\u2019ll go through an example so that you understand how each part of a bubble sort works.<\/p>\n\n\n\n

Python Bubble Sorts<\/h2>\n\n\n\n

A bubble sort compares pairs of adjacent elements and swaps those elements if they are not in order. It is commonly implemented in Python to sort lists of unsorted numbers. Bubble sorts are a standard computer science algorithm.<\/p>\n\n\n\n

By using a bubble sort, you can sort data in either ascending or descending order. Starting from the first element in a list, a bubble sort will compare the first and second elements. If the first element is greater than the second, a swap occurs.\n\n<\/p>\n\n\n\n

This process is repeated until every item in a list is checked. Then, a bubble sort will loop through the list again. This occurs until no more swaps need to be performed.<\/p>\n\n\n\n

When Should You Use a Bubble Sort in Python?<\/h2>\n\n\n\n

Bubble sorts are a good sorting method to use when you\u2019re just starting to learn about sorting algorithms. A bubble sort is a simple way to sort a list of items that do not appear in order.\n\n<\/p>\n\n\n\n

Bubble sorts work best when you have a list with only a few objects. This is because when a bubble sort only has to make a few comparisons, it is very quick. When you need to sort a larger list, there are more efficient algorithms that you can use. Most developers would opt to use a method like an insertion sort to sort a longer list of items.<\/p>\n\n\n\n

Bubble Sort Algorithm Python: Walkthrough<\/h2>\n\n\n\n

Let\u2019s get into the weeds and start to walk through how a bubble sort works. We\u2019ll start with the following list, whose elements appear in the wrong order:<\/p>\n\n\n\n
7<\/td>19<\/td>4<\/td>12<\/td><\/tr><\/tbody><\/table>\n\n\n\n

Our bubble sort starts by comparing the first and second elements in our list. If the first element is greater than the second, then we swap these two elements.\n\n<\/p>\n\n\n\n

In this example, we are going to compare 7 and 19. 7 is not greater than 19, so it stays in the same place. Our list now looks the same as it did before:<\/p>\n\n\n\n
7<\/td>19<\/td>4<\/td>12<\/td><\/tr><\/tbody><\/table>\n\n\n\n

We\u2019ll now go on to compare the second and third elements in our list. 19 is greater than 4, which means that we need to swap them. Our list now looks like this:<\/p>\n\n\n\n
7<\/td>4<\/td>19<\/td>12<\/td><\/tr><\/tbody><\/table>\n\n\n\n

We can now compare the third and fourth items in our list. 19 is greater than 12, so we swap the two numbers:<\/p>\n\n\n\n
7<\/td>4<\/td>12<\/td>19<\/td><\/tr><\/tbody><\/table>\n\n\n\n

Reaching the End of a List<\/h3>\n\n\n\n

Our list is already starting to look sorted. But we\u2019ve reached the end of our list and it is not sorted. What\u2019s going on? Bubble sorts make multiple passes through a list, which means that they keep running until every item in a list is sorted.\n\n<\/p>\n\n\n\n

Our bubble sort will start from the beginning again until the list is sorted. We call each time the list starts sorting values from the beginning a pass<\/strong>. In this example, our bubble sort will compare 7 and 4. 7 is greater than 4, so we swap the elements:<\/p>\n\n\n\n
4<\/td>7<\/td>12<\/td>19<\/td><\/tr><\/tbody><\/table>\n\n\n\n

Our algorithm compares 7 and 12. No swap is necessary, so we\u2019ll move on. We compare 12 and 19. Again no swap is necessary. Now that we\u2019ve reached the end of our list, it\u2019s clear that no more swaps need to be made.\n\n<\/p>\n\n\n\n

Did you notice that our algorithm kept going even after our list sorted? That\u2019s because a bubble sort will continue to swap elements until it compares every item in a list for each item in the list. Our algorithm will not stop until every swap has taken place.<\/p>\n\n\n\n

Bubble Sort Python Program<\/h2>\n\n\n\n

Up until now we\u2019ve been swapping numbers in a table. It\u2019s true that we managed to sort our list, but we don\u2019t have to do this manually. Bubble sorts are a computing algorithm after all; let\u2019s get a computer to run the algorithm for us.<\/p>\n\n\n\n

Let\u2019s begin by writing a Python function<\/a> that sorts a list of numbers in ascending order:<\/p>\n\n\n\n

def sortList(array):\n\tfor item in range(len(array)):\n\t\tfor j in range(0, (len(array) - item - 1)):\n\t\t\tif array[j] > array[j + 1]:\n\t\t\t\t(array[j], array[j + 1]) = (array[j + 1], array[j])<\/pre><\/div>\n\n\n\n
Our algorithm starts with a for loop. This loop iterates through every item in our array. Then, we use another for loop to compare all the items in our array with each other.\n\n<\/p>\n\n\n\n
In our code, we\u2019ve defined a Python \u201cif\u201d statement<\/a> which checks whether a given item is larger than the next item in the list. This \u201cif\u201d statement will perform comparisons such as: <\/p>\n\n\n\n