Python 3 throwing error for exception handling

Question

I started learning python last week and I'm unable to get what's wrong here:

def add(x,y):
    """Adds 2 numbers and returns the result"""
    return x+y

def sub(x,y):
    """Subtracts 2 numbers and returns the result"""
    return x-y


a = int(input("Enter first number"))
b = int(input("Enter second number"))
c = int(input("Enter 1 for subtraction , 2 for addition and 3 for both"))
try:
    if c>3:
        raise ValueError()
except ValueError():
    print ("Wrong choice")
else:
    print ("Your choice is ",c)
if (c==1):
    print ("Subtraction of 2 numbers=",(sub(a,b)))
if (c==2):
    print ("Addition of 2 numbers = ",(add(a,b)))
if (c==3):
    print ("Subtraction of 2 numbers=",(sub(a,b)))
    print ("Addition of 2 numbers = ",(add(a,b)))

If I enter 4 it throws this error:

Traceback (most recent call last):
  File "C:/Program Files (x86)/Python35-32/calculator.py", line 15, in <module>
    raise ValueError()
ValueError

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:/Program Files (x86)/Python35-32/calculator.py", line 16, in <module>
    except ValueError():
TypeError: catching classes that do not inherit from BaseException is not allowed

Answer 1

You are trying to catch an instance of ValueError() , where Python expects you to filter on the type . Remove the call:

except ValueError:
    print ("Wrong choice")