Is it possible to specify exceptions for try statements?

Question

Currently i have this:

try:
    number = int(input('Please enter a number greater than 20'))
    if number > 20:
        print(number)
except ValueError:
    print('We encountered an error. Please try again.')

Is there a way to integrate the if statement into try? Basically so that if the input is not greater than 20 it goes to the except ValueError line. I kind of understand how the try statement works but i can only use it for really simple things, i tried reading up on it and i just got confused. Any help would be greatly appreciated.

I have no idea what that means sorry, could you explain @IgnacioVazquez-Abrams — Anya, Mar 26 '17 at 18:49
http://softwareengineering.stackexchange.com/questions/189222/are-exceptions-as-control-flow-considered-a-serious-antipattern-if-so-why — Ignacio Vazquez-Abrams, Mar 26 '17 at 18:50
An ironic claim in Python, where exceptions are routinely used for flow control. — aghast, Mar 26 '17 at 19:27

score 2 · Accepted Answer · answered Mar 26 '17 at 18:50

You can change your logic around and test if number is invalid and raise ValueError()

try:
    number = int(input('Please enter a number greater than 20'))
    if number <= 20:
        raise ValueError()
    print(number)
except ValueError:
    print('We encountered an error. Please try again.')

You can put a message in the constructor Value('Value <= 20') but you aren't printing out the message in the except clause so no need.
You can wrap this in a forever loop:

while True:
    try:
        number = int(input('Please enter a number greater than 20'))
        if number <= 20:
            raise ValueError()
        print(number)
    except ValueError:
        print('We encountered an error. Please try again.')
    else:
        break

score 0 · Answer 2 · edited May 23 '17 at 12:01

0

You may raise/throw a ValueError exception within the try block as follows:

Manually raising (throwing) an exception in Python

edited May 23 '17 at 12:01

Community

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1

answered Mar 26 '17 at 18:49

Mark

4,249
1
18
27

Ok. Borrowing from the excellent post I cited: `raise ValueError('A very specific bad thing happened')` – Mark Mar 26 '17 at 18:53

Is it possible to specify exceptions for try statements?

2 Answers2