How Can I Ensure Instance-Specific Data in Python Classes?

Instance-Specific Data in Classes

In object-oriented programming, it's possible for instances of a class to share data. This can be undesirable when you want each instance to maintain its own distinct data.

Suppose we have the following class:

class A:
    list = []

When we create instances of this class, all of them share the same list attribute:

>>> x = A()
>>> y = A()
>>> x.list.append(1)
>>> y.list.append(2)
>>> print(x.list)
[1, 2]
>>> print(y.list)
[1, 2]

To avoid this behavior and provide separate instances for each object, we can modify the class declaration:

class A:
    def __init__(self):
        self.list = []

By declaring list within the __init__ method, we create a new instance of list for each new instance of A. This ensures that each instance of A has its own independent list attribute:

>>> x = A()
>>> y = A()
>>> x.list.append(1)
>>> y.list.append(2)
>>> print(x.list)
[1]
>>> print(y.list)
[2]

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