Merge sort in Python

merge_sort.py

# merge() takes two sorted lists and merge them into one sorted list
from heapq import merge
 
def merge_sort(m):
	''' Sort a list in O(n * log(n)) '''
	# If theres only one element in the list, return the list
	if len(m) <= 1:
		return m
	# Split the list into two equal-sized sub-lists
	middle = len(m) / 2
	left = m[:middle]
	right = m[middle:]
	
	# Recursivly sort each half
	left = merge_sort(left)
	right = merge_sort(right)
	
	# Merge the two lists into one sorted list and return it 
	return list(merge(left, right))