Python - how to test if a users input is a decimal number

Question

I am writing a program that needs to check if a users input is a decimal (the users input must be a deciamal number),I was wondering how I could test a varible to see if it contains only a decimal number.

Thanks, Jarvey

Solution 1

U also could use a Try/Except to check if the variable is an integer:

try:    
    val = int(userInput) 
except ValueError:    
    print("That's not an int!")

or a float:

try:    
    val = float(userInput) 
except ValueError:    
    print("That's not an float!")

Solution 2

You can use float.is_integer() method.
Example: data = float(input("Input number"))

if data.is_integer():
  print (str(int(data)) + ' is an integer')
else:
  print (str(data) + ' is not an integer')

Solution 3

I found a way of doing this in python but it doesn't work in a new window/file.

>>> variable=5.5
>>> isinstance(variable, float)
True

>>> variable=5
>>> isinstance(variable, float)
False

I hope this helped.

Solution 4

You can use isinstance:

if isinstance(var, float):
    ...

Solution 5

You can check it by converting to int:

    try:
       val = int(userInput)
    except ValueError:
       print("That's not an int!")

View more solutions

Comments

[hpj]

when I do this it will not allow a decimal number but will allow text. what is a way that I can only allow a decimal number like '0.2' or '1.5' to be accepted but an input like 'hello' will be rejected?

[hpj]

Hi, thanks for the help, this one seemed to work but it also allows charaters and I want is float numbers, do you have any idea how I could stop characters begin accepted?

[Stan Vanhoorn]

How do you mean? If I type in anything other than a number it raises the exception. So in this case it prints: That's not an float!

[hpj]

Thanks, that solved my issue :)