Quick sort, Merge sort, Radix sort, Shell sort in Python

QuickSort:

def quicksort(a,l,r):
    if l < r :
        i = l
        j = r
        pivot = a[i]
        while i < j:
            while a[i] < pivot:
                i = i + 1
            while a[j] > pivot:
                j = j - 1
            if i < j :
                t = a[i]
                a[i] = a[j]
                a[j] = t
        t = a[i]
        a[i] = pivot
        pivot = t
        quicksort(a,l,j-1)
        quicksort(a,j+1,r)
print ("How many Nos. ")
n=int(input())
print ('Enter the Nos. ')
a=[int(input()) for i in range(n)]
print("Accepted Array is ",a)
l=0
r=n-1
quicksort(a,l,r)
print ("Sorted Array is ",a)

MergeSort:

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

    result += left[i:]
    result += right[j:]
    return result

def mergesort(lst):

    if len(lst) <= 1:

        return lst

    middle = int(len(lst) / 2)
    left = mergesort(lst[:middle])
    right = mergesort(lst[middle:])
    return merge(left, right)
print ('How many Nos.')
n=int(input())
print ('Enter the Nos. -')
a=[int(input()) for i in range(n)]
print ('Sorted Array is -')
mergesort(a)
print (a)

ShellSort:

def shell(alist):

         count=len(alist)//2

         while count>0:

                   for start in range(count):

                             gap(alist,start,count)

                   print("increment", count,"list is",alist)

                   count=count//2

def gap(alist,start1,gap1):             

         for i in range (start1+gap1,len(alist),gap1):

                   current=alist[i]

                   pos=i

                   while pos>=gap1 and alist[pos-gap1]>current:

                             alist[pos]=alist[pos-gap1]

                             pos=pos-gap1

                   alist[pos]=current

alist=[2,0,5,9,1]

shell(alist)

print(alist)

RadixSort:

def r(a,k,i):

    c = i+1

    d = 1

    for s in range(c):

        re = (a[k] / d) % 10

        d *= 10

    return re

def radix(a,l,n):

    a1,b,c,d,e,f,g,h,i,j=[],[],[],[],[],[],[],[],[],[]

    buck=[a1,b,c,d,e,f,g,h,i,j]

    for i in range (l):

        for k in range (n):

            t = r(a,k,i)

            buck[t].append(a[k])

        a = []

        for s in range (10):

            sz = len(buck[s])

            for t in range (sz):

                a.append(buck[s][t])

            buck[s] = []

    return a

n = int(input( "Enter Total No of Elements - "))

a = [int(input())for i in range (n)]

lr = a[0]

for i in range (n):

    if a[i] > lr:

        lr = a[i]

l = len(str(lr))

print ('Sorted Array is -')

print ("a",radix(a, l, n))