reusing a variable defined in a python class

Question

Let's say I define a class. I have a fun method, where I create self.x. I want to use self.x in a different method (reuse). How could I do that? Because I tried what I wrote and didn't work. Thanks!

class test:
    def __init__(self,t):
       self.t = t
    def fun(self):
       self.x = self.t+1
    def reuse(self):
       self.y = self.x

Unless self.fun() is ever executed, self.x is not defined, so you'll need to ensure that self.fun() has been called atleast once prior to calling self.reuse() — rdas
– rdas, Commented Apr 17, 2020 at 5:58
so it would have to something like this: self.y = self.fun()? — Schach21
– Schach21, Commented Apr 17, 2020 at 5:59
self.fun() doesn't return anything. So you'll just need to add self.fun() before the self.y = self.x — rdas
– rdas, Commented Apr 17, 2020 at 6:23
@rdas If he adds self.fun() before self.y = self.x it calls the self.fun() every time he calls self.reuse(), which can modify the contents. — Prudhvi
– Prudhvi, Commented Apr 17, 2020 at 6:29

Prudhvi · Accepted Answer · 2020-04-17 06:00:16Z

1

You need to create all the variables in the __init__ method. Try this:

class test:
    def __init__(self,t):
       self.t = t
       self.x = 0
       self.y = 0
    def fun(self):
       self.x = self.t+1
    def reuse(self):
       self.y = self.x

answered Apr 17, 2020 at 6:00

Prudhvi

1,1251 gold badge7 silver badges18 bronze badges

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

5 Comments

Schach21 Over a year ago

Thanks but that's not what I want. I made a simplistic example, but in fun(), I compute many things and that I want to reuse and not compute again. Let me ask another question though. In fun, what is the difference between making the assigment self.x = self.t+1 and x = self.t+1. I think I know but I'd like the confirmation of someone more knowledgeable.

Thierry Lathuille Over a year ago

x = self.t+1 creates a local variable x in your method, that gets discarded when the method exits. self.x = self.t+1 updates the value of your instance's x attribute. But according to this last question, it seems that you over-simplified the example in your question, and that it doesn't really ask what you want...

Prudhvi Over a year ago

When you use self.x = self.t+1 it will update the value of the class variable. When you use x = self.t+1 it will create a local variable to that function, which you can't access outside.

Schach21 Over a year ago

Wait a minute. I think your answer is correct. If I write the class the way you did. is self.y = self.x = self.t+1 ? In other words, self.y = self.t+1? or self.y = 0? I guess I can just run this and see what happens.

Prudhvi Over a year ago

When you mention self.x = 0 in __init__ it will just execute once once when the instance is created. when you call other functions it will return use the values which are calculated before.

Collectives™ on Stack Overflow

reusing a variable defined in a python class

1 Answer 1

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related