Sorting Algorithms in Python

Sorting Algorithms in Python is a core Python concept covering sorting Algorithms in Python: --8<: "core-logic/sorting-algorithms.md" This topic is essential for academic learning, board exam preparation, and developing optimized real-world code.

Sorting Algorithms

Sorting is the process of arranging items in a specific order (usually ascending or descending).

Common Sorting Strategies

Bubble Sort: Repeatedly swap adjacent elements if they are in the wrong order. Small values "bubble" to the top.
Selection Sort: Find the smallest element and move it to the beginning. Repeat for the rest.
Insertion Sort: Build the sorted list one item at a time by inserting each new item into its correct position.
Merge Sort: Divide the list into halves, sort each half, and then merge them back together. (Fast and reliable).
Quick Sort: Pick a "pivot" element and partition the list around it. (Very fast in practice).

Complexity

In computer science, we measure how "expensive" an algorithm is using Big O Notation. Simple sorts (Bubble, Selection) are usually $O(n^2)$, while advanced sorts (Merge, Quick) are $O(n \log n)$.

1. Bubble Sort

def bubble_sort(arr):
    n = len(arr)
    for i in range(n):
        for j in range(0, n-i-1):
            if arr[j] > arr[j+1]:
                arr[j], arr[j+1] = arr[j+1], arr[j] # Swap
    return arr

print(bubble_sort([64, 34, 25, 12, 22]))

2. Quick Sort (Recursive)

def quick_sort(arr):
    if len(arr) <= 1:
        return arr
    pivot = arr[len(arr) // 2]
    left = [x for x in arr if x < pivot]
    middle = [x for x in arr if x == pivot]
    right = [x for x in arr if x > pivot]
    return quick_sort(left) + middle + quick_sort(right)

print(quick_sort([64, 34, 25, 12, 22]))

Python's Built-in Sort: Timsort

In real-world Python development, we rarely write our own sorting algorithms. Python uses a highly optimized algorithm called Timsort (a hybrid of Merge Sort and Insertion Sort).

# Modifies the original list
mylist = [5, 2, 9, 1]
mylist.sort()

# Returns a new sorted list
newlist = sorted([5, 2, 9, 1])

Industry Fact

Python's sort() and sorted() are written in C and are extremely fast. Always use them unless you are explicitly asked to implement a specific algorithm for an exam or interview.

Sorting Algorithms in Python