How do I update a variable value across modules Python?

Question

I have a main script and I am importing another module with a class in it. When I instantiate the class one of the arguments is y and therefore I have an equivalent self.y = y in the __init__ method. Now the problem is that in the main script I have a for loop that changes the y value and calls the method 'live_plotting' from the same class. I usually have to pass in the y value as an argument again and have another self.y = y inside the method. This is not neat, is there any way of updating self.y across modules without having to pass in as an argument again? I thought of using pointers but apparently everything is a pointer in python. Can anyone offer an alternative solution?

We won't be able to help you with such a vague question. Provide the code you've written so far, your expected input and output, and a description of why it doesn't work. — Benjamin Hodgson
– Benjamin Hodgson, Commented Jul 19, 2016 at 11:14
@BenjaminHodgson I cant provide the entire code because it too much. The basic structure is there and I'm asking a question regarding updating variables across modules not about my code. — marjak
– marjak, Commented Jul 19, 2016 at 12:36
Also the code requires knowledge of matplotlib, so a regular programmer wouldn't understand it. So Im asking a general question about modules. — marjak
– marjak, Commented Jul 19, 2016 at 12:37
You don't want to pass y as an argument from the live_plotting(self,BOOLEAN, y ) function ? — pwnsauce
– pwnsauce, Commented Jul 19, 2016 at 13:17
If I understand correcly : you want that each time y is modified, self.y is also modified? maybe instead of using y you just use InstanceName.y where instanceName is the name of the object you instanciated. Mutator have to be defined in the class : def set_y(self,y) : self.y=y and you use it : InstanceName.set_y(value) — pwnsauce
– pwnsauce, Commented Jul 19, 2016 at 13:31

Zpooks · Accepted Answer · 2016-07-19 13:45:26Z

2

I'm not really sure if it's what you want, but from my understanding you want to update the value of self.y without a method?

This would be done by executing

object_name.y = new_value

where object_name is the name you gave the instance of your Class, seeing as self variables declared in the __init__ are attributes that belong to that instance of the class.

edited Jul 19, 2016 at 13:45

answered Jul 19, 2016 at 13:30

Zpooks

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pwnsauce · Accepted Answer · 2016-07-19 13:51:34Z

From what i've understand, mutator arn't what you are looking for. A mutator is a function within a class that access an attribut and modify it's value.

I think in your code, you want to use y as if self.y and y where linked to each others. But when you give y as an argument to a function, then self.y = y the y in the function is a copie of the y you passed as an argument. then self.y = y take the value of the copied y and store it in self.y.

After instanciating your object :

my_instance = class(x,y)
#if you want to modify my_instance.y
my_instance.y = value

or with a mutator in the class :

def set_y(self,value):
    self.y=value

then in your main when you want to modify y :

my_instance.set_y(value)

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