added recursive merge sort in python

Sorting Algorithm/MergeSort_Recursively/RecMergeSort.py

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+#itai192
+#a method that merges two ordered list
+def Merge(l1, l2):
+    l3=[]
+	#until one list is empty
+    while(len(l1)>0 and len(l2)>0):
+	#add the lowest value between the two lists into the third list and remove it from the list it came from
+        if (l1[0]<l2[0]):
+            l3.append(l1.pop(0))
+        else:
+            l3.append(l2.pop(0))
+	#when one of the two lists is empty, empty the other list into the third list and return the third list
+    while(len(l1)>0):
+        l3.append(l1.pop(0))
+    while(len(l2)>0):
+        l3.append(l2.pop(0))
+    return l3
+#the recursive merge sort method
+def MergeSortRec(lis,start,end):
+    length=end-start+1
+	#if the length is one return a list with one item in it
+    if(length==1):
+        return [lis[start]]
+	#if the list has two items, return a list containing the two items in order
+    if(length==2):
+	#if the list is in order return it the same way
+        if(lis[start]<lis[end]):
+            return [lis[start],lis[end]]
+	#if the list isn't in order reverse the order and return it
+        else:
+            return[lis[end],lis[start]]
+	#if the list has more than 2 items in it, split the list into 2, and sort them, then merge them
+    mid= (start+end)//2
+    l1 = MergeSortRec(lis,start,mid)
+    l2 = MergeSortRec(lis,mid+1,end)
+    return Merge(l1,l2)
+#an help method to use the recursive merge(i'm new to python so I don't know if there is a better way to do it)
+def MergeSort(lis):
+    return MergeSortRec(l1,0,len(lis)-1)
+
+