What is the purpose of using __slots__ in Python and how does it differ from regular class attributes?

__slots__ in Python is used to restrict the set of attributes that instances of a class can have. This allows:

• Saving memory, as a __dict__ dictionary is not created for each object.
• Speeding up attribute access.

The difference from regular attributes is that when using __slots__, Python knows in advance which attributes are allowed and does not create a dynamic attribute dictionary.

Example:

class Point:
    __slots__ = ('x', 'y')

    def __init__(self, x, y):
        self.x = x
        self.y = y

p = Point(1, 2)
p.x = 10  # works
# p.z = 3  # will raise AttributeError because 'z' is not in __slots__

Thus, __slots__ is useful for memory optimization and preventing accidental addition of new attributes.