Python init without executing a variable

Question

I am looking for a way to init a variable in a class. This variable is dependent of other variables that I init in the same class too. Here is an example.

Class class():
    def __init__()
        self.a = None
        self.b = None
        self.sum = self.a + self.b

    def change_a_and_b()
       self.a = input("a = ")
       self.b = input("b = ")

    def print_sum()
        print(self.sum)

This is a simplified example. In my program self.sum is a complicated calculation which I want to use like a "shortcut" so I don't need to write it a lot of times. The problem is I input the variables after the init function. I just don't want to execute self.sum = self.a + self.b when I run __init__. I think there is a do_thing parameter, but I don't know how to use it.

Because it is ment to be a calculation I use in different function for the same class — BrockenDuck
– BrockenDuck, Commented Nov 27, 2018 at 9:38
So? You will always have to use it after you call change_a_and_b... — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Nov 27, 2018 at 9:49

cha0site · Accepted Answer · 2018-11-27 08:41:01Z

4

You can make sum a property:

class my_class():
    def __init__(self)
        self.a = None
        self.b = None

    @property
    def sum(self):
        return self.a + self.b

    def change_a_and_b(self)
       self.a = input("a = ")
       self.b = input("b = ")

    def print_sum(self)
        print(self.sum)

answered Nov 27, 2018 at 8:41

cha0site

10.8k3 gold badges36 silver badges52 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

BrockenDuck Over a year ago

Can I still access it like a normal self.variable ?

cha0site Over a year ago

Yup, exactly like you see in the example (try it out). That's the point of a property, it's a kind of syntactic sugar for treating a function like a variable.

BrockenDuck Over a year ago

Do I still access it with self.sum or not ?

cha0site Over a year ago

Yes, you do. self.sum, and not self.sum().

Collectives™ on Stack Overflow

Python init without executing a variable

1 Answer 1

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related