# [Tutor] Additional help

Ghadir Ghasemi ghasemmg01 at leedslearning.net
Sun Feb 10 21:29:23 CET 2013

```Hi guys, I wondered if you knew what I could add to this code so that when the user enters 1 from the menu and then doesn't enter a valid binary number the program should ask them over and over again until valid binary number is entered.
here is the code:

def show_menu():
print("=======================")
print("1-binary to denary")
print("2-denary to binary")
print("3-exit")
print("=======================")

while True:
show_menu()

choice = input("please enter an option: ")

if choice == '1':
binary = input("Please enter a binary number: ")
denary = 0
place_value = 1

for i in binary [::-1]:
denary += place_value * int(i)
place_value *= 2

print("The result is",denary)

elif choice == '2':
denary2 = int(input("Please enter a denary number: "))
remainder = ''
while denary2 > 0:
remainder = str(denary2 % 2) + remainder
denary2 >>= 1
print("The result is",remainder)

elif choice == '3':
break

elif choice not in '1' or '2' or '3':
print("Invalid input-try again!")

Thanks
```

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