# [Tutor] Binary/Decimal convertor

Alan Gauld alan.gauld at btinternet.com
Sat Jan 12 01:59:13 CET 2013

```On 11/01/13 21:51, Ghadir Ghasemi wrote:
> Hi, I made a program called binary/denary convertor.

> Can anyone tell me about how I could stop the user entering a binary
> number with more than 8 numbers or 8 bit

Why would you want to? Your code can handle much bigger binary numbers,
why limit the user to 8 bits?

> Here is the code. I started off by entering 'len' function.

> num1 = int(input('please enter the first 8 bit binary number: '),2)

Here hyou read the number as a string and already convert it to a real
number in Python. So the conversion from  binary has already happened
regardless of how long the string was.

> if len(num1) > 8:
>      print("please enter an 8 bit binary number")

You now try to see how long the number is, but numvers don;t have a length.
So to do what you claim you want you need to do the len() check before
you do the inty() conversion.
Something like:

num1 = input('please enter the first 8 bit binary number: ')
if len(num1) > 8:
print("please enter an 8 bit binary number")
else:
num = int(num,2)

Then put that in while a loop that repeats until the length is <=8

> return int(num1,2)

And here you return which would terminate your function except you don't
have a function so it will give a syntax error. And trying to convert a
num as a binary won't work because its already stored internally as a
binary number. This only works if you still have the string as described
above.

> num2 = int(input('please enter the second 8 bit binary number: '),2)

And this doesn't do any len() checks....

> print('the result is', bin(result)[2:])