Python 3.6 validating an integer input

Question

I am using Python 3.6 currently and my code currently is asking a user to input 2 integers and convert them into binary form, this is not a problem, the issue that I have is when it asks the user to input a number, if they put anything other than an integer, it will break the code and come up with an error, is there a specific few lines of code that will ensure that errors will not display if letters or floats are inputted?

def add():

    Num1 = int(input("Input the first number between 0 and 255, the calculated answer must not be above 255: "))
    Num2 = int(input("Input the second number between 0 and 255, the calculated answer must not be above 255: "))

I have tried one method which was:

if type(Num1) != int:
    print("Please input a number")
    add()

However I still get errors when testing the code.

I would like the code to detect that a string or float has been inputted, then reload the "def" function without giving a syntax error.

This is the print result:

Use exception handling to catch the error. Do you know how to use `try`? — Carcigenicate, Dec 06 '17 at 15:51
I do not know how to use try, I have never used it in any of my Python codes before — PurpleWombat, Dec 06 '17 at 15:53
Read up on using it. It's needed here, and is necessary knowledge for general programming anyway. — Carcigenicate, Dec 06 '17 at 15:53
Technically there are other ways of solving it, but using try/catch is the most straightforward. — Carcigenicate, Dec 06 '17 at 15:54
Once you understand how it works, you just need to `catch` the `ValueError` that `int` throws. — Carcigenicate, Dec 06 '17 at 15:55
while True: try: Num1 = int(input("Please enter a number between 0 and 255, note that the final sum cannot be above 255: ")) Num2 = int(input("Please enter a number betweem 0 and 255 note that the final sum cannot be above 255: ")) except ValueError: print("ERROR Please input a decimal between 0 and 255.") continue else: break — PurpleWombat, Dec 06 '17 at 16:42

offwhitelotus · Answer 1 · 2017-12-06T16:05:41.403

0

This is the gist of how to get an integer from the command line. It works using a while loop and try/except statements. You can add the checks for the integer range. You can use this code to create a function, which can be called twice for your particular problem.

n = None
while True:
    n = input('enter an integer')
    try:
        n = int(n)
        break
    except:
        continue

edited Dec 06 '17 at 16:05

answered Dec 06 '17 at 15:59

offwhitelotus

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Python 3.6 validating an integer input

1 Answers1