Airline after some corrections

Airline-Corrected.py

firstclass = [0]*8        #list that stores first class data
economyclass = [0]*8      #list that stores economy class data
booked = {}                           #Stores names and seat numbers of booked people
 
def displayseats():                   #This will display seats in a formatted way
    print("First Class  Economy Class")
   
    for each in range(0,4):
        if firstclass[each] == 0:
            print("(" +str(each+1) + ")", end='')
        else:
            print("(X)", end='')
        print("     ",end='')
        if(firstclass[each+4] == 0):
            print("(" + str(each+5) + ")",end='')
        else:
            print("(X)",end='')
        print(" ",end='')
        if economyclass[each] == 0:
            print("[" +str(each+1+8) + "]",end='')
        else:
            print("(X)", end='')
        print("       ",end='')
        if(economyclass[each+4] == 0):
            print("[" + str(each+5+8) + "]")
        else:
            print("[X]")
 
def bookseat(name):
    displayseats()                            #This will book the seat
    a = input("Enter 1 for First Class and 2 for Economy Class: ")
    while (not a.isdigit()) or (int(a) != 1 and int(a) != 2):
        a = input("Please enter a valid option: ")
    clas = int(a)
    if clas==1:
        stringseatno= input("Enter the seat number(1-8): ")
        while not stringseatno.isdigit() or int(stringseatno) not in range(1,9) or int(stringseatno) in booked.values():
            stringseatno = input("Please enter valid seat number: ")
            while not stringseatno.isdigit():
                stringseatno = input("Enter a valid number: ")
        seatno = int(stringseatno)
        firstclass[seatno-1] = 1
        booked[name] = seatno
    elif clas==2:
        stringseatno= input("Enter the seat number(9-16): ")
        while not stringseatno.isdigit() or int(stringseatno) not in range(9,17) or int(stringseatno) in booked.values():
            stringseatno = input("Please enter valid seat number: ")
            while not stringseatno.isdigit():
                stringseatno = input("Enter a valid number: ")
        seatno = int(stringseatno)
        economyclass[seatno-9] = 1
        booked[name] = seatno
        
def showbooked():                       #This will show the booked seat
    print("Seat Number     Name")
    for key,value in booked.items():
        print(str(value) + " "*13 + str(key))
       
def showmenu():
    name = input("Enter your name: ")
    bookseat(name)                         #This is the main driver function which calls others!
    while True:
        displayseats()
        print("1.Book Seat\n2.Show Booked\n3.Exit\n Enter your option: ")
        a = input()
        while (not a.isdigit()) or ( int(a) != 1 and int(a) != 2 and int(a) != 3):
            a = input("Please enter a valid option: ")
        x = int(a)
        if x == 1:
            name = input("Enter your name: ")
            bookseat(name)
        elif x == 2:
            showbooked()
        elif x == 3:
            break
    return
       
showmenu()