Improved MergeSort.py

* Added Python3 support

MergeSort.py

@@ -1,36 +1,59 @@
-def mergeSort(alist):
-    print("Splitting ",alist)
-    if len(alist)>1:
-        mid = len(alist)//2
-        lefthalf = alist[:mid]
-        righthalf = alist[mid:]
-        mergeSort(lefthalf)
-        mergeSort(righthalf)
-        i=0
-        j=0
-        k=0
-        while i < len(lefthalf) and j < len(righthalf):
-            if lefthalf[i] < righthalf[j]:
-                alist[k]=lefthalf[i]
-                i=i+1
+import sys
+
+
+def merge_sort(alist):
+    print("Splitting ", alist)
+    if len(alist) > 1:
+        mid = len(alist) // 2
+        left_half = alist[:mid]
+        right_half = alist[mid:]
+        merge_sort(left_half)
+        merge_sort(right_half)
+        i = j = k = 0
+
+        while i < len(left_half) and j < len(right_half):
+            if left_half[i] < right_half[j]:
+                alist[k] = left_half[i]
+                i += 1
             else:
-                alist[k]=righthalf[j]
-                j=j+1
-            k=k+1
+                alist[k] = right_half[j]
+                j += 1
+            k += 1
 
-        while i < len(lefthalf):
-            alist[k]=lefthalf[i]
-            i=i+1
-            k=k+1
+        while i < len(left_half):
+            alist[k] = left_half[i]
+            i += 1
+            k += 1
 
-        while j < len(righthalf):
-            alist[k]=righthalf[j]
-            j=j+1
-            k=k+1
-    print("Merging ",alist)
+        while j < len(right_half):
+            alist[k] = right_half[j]
+            j += 1
+            k += 1
+    print("Merging ", alist)
+    return alist
 
-print("Enter numbers seprated by space")
-s = input()
-numbers = list(map(int, s.split()))
-mergeSort(numbers)
 
+def main():
+    # Python 2's `raw_input` has been renamed to `input` in Python 3
+    if sys.version_info.major < 3:
+        input_function = raw_input
+    else:
+        input_function = input
+
+    try:
+        print("Enter numbers separated by spaces:")
+        s = input_function()
+        inputs = list(map(int, s.split(' ')))
+        if len(inputs) < 2:
+            print('No Enough values to sort!')
+            raise Exception
+
+    except Exception as e:
+        print(e)
+    else:
+        sorted_input = merge_sort(inputs)
+        print('\nSorted list (min to max): {}'.format(sorted_input))
+
+if __name__ == '__main__':
+    print('==== Merge Sort ====\n')
+    main()