Merge Sort using Python

Merge sort contains two phases.
1. Partition phase
2. Merge phase

In partition phase the list is broken in to parts by calculating mid point.
In merging phase the list is merged by sorting. Finally a sorted list is obtained.

 Merge sort is a divide and conqure algorithm. Divide and Conqure means divide the problem in to small parts, solve these sub parts and finally combine the solutions to get the final answer.

Source Code:

def part(a,l,r):
    if l<r:
        m=(l+r)//2
        part(a,l,m)
        part(a,m+1,r)
        merge(a,l,m,r)
    #print(b)
def merge(a,l,m,r):
    b=[]
    k=0
    i=l
    j=m+1
    while i<=m and j<=r:
        if a[i]<a[j]:
            b.append(a[i])
            k=k+1
            i=i+1
        else:
            b.append(a[j])
            k=k+1
            j=j+1
    while i<=m:
        b.append(a[i])
        k=k+1
        i=i+1
    while j<=r:
        b.append(a[j])
        k=k+1
        j=j+1
    for i in range(k):
        a[l]=b[i]
        l=l+1
a=[ ]
n=int(input("enter n"))
for i in range(n):
    a.insert(i,int(input()))
l=0
r=n-1
part(a,l,r)
print(a)
   
Output:   

Python 3.4.0 (v3.4.0:04f714765c13, Mar 16 2014, 19:24:06) [MSC v.1600 32 bit (Intel)] on win32
Type "copyright", "credits" or "license()" for more information.
>>> ================================ RESTART ================================
>>>
enter n5
10
5
3
7
2
[2, 3, 5, 7, 10]
>>>