Heap

class heapexception(Exception):
    pass

class Heap:
    def __init__(self,maxsize=10):
        self.a=[None]*maxsize
        self.n=0
        self.a[0]=9999

    def insertnode(self,value):
        self.n+=1
        self.a[self.n]=value
        self.restoreUpKey(self.n)

    def restoreUpKey(self,i):
        key=self.a[i]
        iparent=i//2
        while self.a[iparent]<key:
            self.a[i]=self.a[iparent]
            i=iparent
            iparent=i//2
        self.a[i]=key

    def deletenode(self):
        if self.n==0:
            raise heapexception("Heap is empty, Nothing to be deleted!")
        maxVal=self.a[1]
        self.a[1]=self.a[self.n]
        self.n-=1
        self.restoreDownKey(1)
        return maxVal

    def restoreDownKey(self,i):
        key=self.a[i]
        lchild=2*i
        rchild=(2*i)+1
        #for odd no.of nodes
        while rchild<=self.n:
            if(key>=self.a[lchild] and key>=self.a[rchild]):
                self.a[i]=key
                return
            else:
                if self.a[lchild]>self.a[rchild]:
                    self.a[i]=self.a[lchild]
                    i=lchild
                else:
                    self.a[i]=self.a[rchild]
                    i=rchild
            lchild=2*i
            rchild=lchild+1

        #for even no of nodes
        if lchild==self.n and key<self.a[lchild]:
            self.a[i]=self.a[lchild]
            i=lchild
        self.a[i]=key

    def displayHeap(self):
        if self.n==0:
            print("Heap is empty")
            return
        print("Heap size: ",self.n)
        for i in range(1,self.n+1):
            print(self.a[i],'',end='')
        print()

h=Heap(20)
while True:
    print("1.Insert in Heap")
    print("2.Delete root")
    print("3.Display")
    print("4.Exit")
    choice=int(input("Enter your choice: "))
    if choice==1:
        value=int(input("Enter a value for insertion: "))
        h.insertnode(value)
    elif choice==2:
        print("Deleted max/root value is: ",h.deletenode())
    elif choice==3:
        h.displayHeap()
    elif choice==4:
        break
    else:
        print("Wrong choice!")