Validating if variable is int

Question

I have a script to create vlan in cisco switches, and I need the user to input a number to the script.

I'm having trouble to make the script validate if the input is a number(must be int) and if the number is inside the range 2~4094, before it moves to the next steps.

I already wrote the rest of the script.

Try `str.isdigit()`. For example, `"1".isdigit()` returns `True` and `"1.1".isdigit()` returns `False`, then you can check its range. — Tianbo Ji, May 27 '19 at 15:46
@OlvinRoght What is your Python version? I tested `"½".isdigit()` on Python 3.7.3 and 2.7.10, both return `False`. — Tianbo Ji, May 27 '19 at 15:57
@TianboJi, sorry, this example is for `isnumeric()`. `'³'.isdigit()` this will return True for both python versions. The idea is for validation before type cast to int `isdecimal()` should be used. — Olvin Roght, May 27 '19 at 16:03
@OlvinRoght you are correct, `'³'.isdigit()` does return `True`. `isdecimal()` is a better solution for this question. — Tianbo Ji, May 27 '19 at 16:06

score 3 · Answer 1 · answered May 27 '19 at 15:44

3

This should work:

def validate(num):
    try:
        n = int(num)
        return 2 <= n <= 4094
    except:
        return False

The above function returns True if the number is an integer in the specified range, False otherwise.

answered May 27 '19 at 15:44

Óscar López

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thanks... but when I try you example... if the user input something like TESTE besides an int, the scripts goes on. – Douglas May 27 '19 at 15:59
We'd need to know how you're calling your script, and how you're using my function. You need to provide a lot more details for people to be able to help you... – Óscar López May 27 '19 at 16:02

score 0 · Answer 2 · edited May 27 '19 at 15:48

0

try:
    val = int(user_input)
    print("user input is an int")
except ValueError:
    print("user_input is not an int")

edited May 27 '19 at 15:48

vinzee

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answered May 27 '19 at 15:46

Suresh Parimi

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Olvin Roght · Answer 3 · 2019-05-27T15:53:23.947

0

You can use str.isdecimal() to check if string contains only digits.

inp = input("Enter number: ")
if inp.isdecimal():
    n = int(inp)
else:
    print("Not a number")

If you need function:

def validate(inp):
    return isinstance(inp, str) and inp.isdecimal()


inp = input("Enter number: ")
print(validate(inp))

edited May 27 '19 at 15:53

answered May 27 '19 at 15:47

Olvin Roght

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balderman · Answer 4 · 2019-05-27T15:59:47.587

0

When the function below return True, you can do the Math you need to do with the number.

def as_int_in_range(value,range):
    try:
        value = int(value)
        if value >= range[0] and value <= range[1]:
            return True,value 
        else:
            return False,None 
    except ValueError:
        return False,None

is_int,val = as_int_in_range('12',(10,100))
if is_int:
    # do something with 'val' assuming it is int in the range
else:
    # do something  else

edited May 27 '19 at 15:59

answered May 27 '19 at 15:49

balderman

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thank you... but if the input is not a int, I need the script to ask again for the value, until the provided input is a int – Douglas May 27 '19 at 15:57
@Douglas, apply `while` loop. Check [this](https://stackoverflow.com/a/56256888/10824407) answer, I've provided some examples there. – Olvin Roght May 27 '19 at 16:06

Validating if variable is int

4 Answers4