Python variable assignment between different methods

Question

I would like to define a class variable in Python and then modify its value calling two different methods in this way:

class MyClass:   
    # Variable x definition
    nonlocal x
    
    def Method1():
        nonlocal x
        x = 1
        print('X VALUE: ', x)
        
    def Method2():
        nonlocal x
        print('X VALUE BEFORE NEW ASSIGNMENT: ', x)
        x = 2
        print('X VALUE NEW ASSIGNMENT: ', x)
        
c = MyClass()
c.Method1()
c.Method2()

I get this error at line 10: nonlocal x 'SyntaxError: no binding for nonlocal 'x' found'. What's wrong? Thanks a lot.

A simple class variable would seem like a better solution for this isolated example. — tripleee
– tripleee, Commented Sep 16, 2022 at 12:47
Even if MyClass were a function rather than a class, you would only use nonlocal in the two nested functions to refer to a variable outside their scope, not in the function whose variable is being accessed. (You would still need to ensure that x was actually defined so that nonlocal would know which scope contained x.) — chepner
– chepner, Commented Sep 16, 2022 at 13:00

Mark Reed · Accepted Answer · 2022-09-16 13:33:22Z

2

nonlocal only works in nested functions. For top-level methods like this, you could just use global.

But it would seem to make more sense in this case to make x a static/class attribute instead.

Unrelated to your question, calls to your two methods will fail because you didn't declare them with the self parameter.

edited Sep 16, 2022 at 13:33

answered Sep 16, 2022 at 12:51

Mark Reed

96k17 gold badges149 silver badges189 bronze badges

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

Comments

3dSpatialUser · Accepted Answer · 2022-09-16 12:57:39Z

0

I am not sure what you try to do, since you give the functions no input the values of x will always be the same but see this:


class MyClass:   
    # Variable x definition
    def __init__(self):
        self.x = None
    
    def Method1(self):
        self.x = 1
        print('X VALUE: ', self.x)
        
    def Method2(self):
        print('X VALUE BEFORE NEW ASSIGNMENT: ', self.x)
        self.x = 2
        print('X VALUE NEW ASSIGNMENT: ', self.x)
        
c = MyClass()
c.Method1()
c.Method2()
c.Method2()

output:

X VALUE:  1
X VALUE BEFORE NEW ASSIGNMENT:  1
X VALUE NEW ASSIGNMENT:  2
X VALUE BEFORE NEW ASSIGNMENT:  2
X VALUE NEW ASSIGNMENT:  2

edited Sep 16, 2022 at 12:57

answered Sep 16, 2022 at 12:47

3dSpatialUser

2,4061 gold badge13 silver badges23 bronze badges

Collectives™ on Stack Overflow

Python variable assignment between different methods

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related