I m getting a error name ch is not defined

Question

class Library:
    def __init__(self):
        self.bookname=""
        self.author=""
    def getdata(self):
        self.bookname = input("Enter Name of the Book: ")
        self.author = input("Enter Author of the Book: ")
    def display(self):
        print("Name of the Book: ",self.bookname)
        print("Author of the Book: ",self.author)
        print("\n")
        book=[] #empty list
        ch = 'y'
while (ch=='y'):
    print("1. Add New Book \n 2.Display Books")
    resp = int(input("Enter your choice : "))
if(resp==1):
    L=Library()
    L.getdata()
    book.append(L)
elif(resp==2):
    for x in book:
        x.display()
else:
    print("Invalid input....")
    ch = input("Do you want continue....")