Some sorting algorithm coding practices in Python.

sortings.py

# bubble sort
def bubble_sort(arr):
	arr_len = len(arr)
	for i in range(arr_len - 1, 0, -1):
		for j in range(i):
			if arr[j] > arr[j + 1]:
				arr[j], arr[j + 1] = arr[j + 1], arr[j]

a = [2,5,1,8,-2,0,9,2]
bubble_sort(a) # inplace sorting

# selection sort swap max
def select_sort_swap_max(arr):
	arr_len = len(arr)
	for i in range(arr_len - 1, 0, -1):
		max_index = 0
		for j in range(i + 1):
			if arr[j] > arr[max_index]:
				max_index = j
		arr[i], arr[max_index]= arr[max_index], arr[i]

a = [2,5,1,8,-2,0,9,2]
select_sort_swap_max(a) # inplace sorting

def select_sort_swap_max_2(array):
    """
    input: int[] array
    return: int[]
    """
    # write your solution here
    # swap max
    # MISTAKE!!! if not array: # CAUTION: edge case!!!
    if array:
      for i in range(len(array) - 1, 0, -1):
        max_index = 0
        for j in range(1, i + 1):
          if array[j] > array[max_index]:
            max_index = j
        array[i], array[max_index] = array[max_index], array[i]
    return array



# selection sort swap min - MISTAKE
# def select_sort_swap_min(arr):
# 	arr_len = len(arr)
# 	for i in range(arr_len - 1, 0, -1):
# 		min_index = 0
# 		for j in range(i + 1):
# 			if arr[j] < arr[min_index]:
# 				min_index = j
# 		arr[arr_len - i], arr[min_index]= arr[min_index], arr[arr_len - i]

# a = [2,5,1,8,-2,0,9,2]
# select_sort_swap_min(a) # inplace sorting

# selection sort swap min
def select_sort_swap_min(arr):
	len_arr = len(arr)
	for i in range(len_arr):
		# least_index = 0
		least_index = i
		for j in range(i, len_arr):
			if arr[j] < arr[least_index]:
				least_index = j
		arr[i], arr[least_index] = arr[least_index], arr[i]
a = [2,5,1,8,-2,0,9,2]
select_sort_swap_min(a) # inplace sorting

# Insertion Sort

# Merge Sort
def merge(left, right):
    merged_list = []
    i = 0
    j = 0
    while i < len(left) and j < len(right):
      if left[i] < right[j]:
        merged_list.append(left[i])
        i += 1
      else:
        merged_list.append(right[j])
        j += 1
    if i == len(left):
      merged_list = merged_list + right[j:]
    else:
      merged_list = merged_list + left[i:]
    return merged_list


def mergeSort(array):
    """
    input: int[] array
    return: int[]
    """
    if not array or len(array) == 1:
      return array
    middle = (len(array) + 1) // 2
    return merge(mergeSort(array[:middle]), mergeSort(array[middle:]))
    # return mergeSort(merge(array[:middle], array[middle:]))