@property

class Circle:
    def __init__(self, radius):
        self._radius = radius

    @property
    def radius(self):
        return self._radius

# Example usage:
c = Circle(5)
print(c.radius)  # Output: 5

class Circle:
    def __init__(self, radius):
        self._radius = radius

    @property
    def radius(self):
        return self._radius

    @radius.setter
    def radius(self, value):
        if value < 0:
            raise ValueError("Radius cannot be negative")
        self._radius = value

# Example usage:
c = Circle(5)
print(c.radius)  # Output: 5
c.radius = 10
print(c.radius)  # Output: 10
# c.radius = -1  # Uncommenting this line will raise a ValueError

class Circle:
    def __init__(self, radius):
        self._radius = radius

    @property
    def radius(self):
        return self._radius

    @radius.setter
    def radius(self, value):
        if value < 0:
            raise ValueError("Radius cannot be negative")
        self._radius = value

    @radius.deleter
    def radius(self):
        del self._radius

# Example usage:
c = Circle(5)
print(c.radius)  # Output: 5
del c.radius
# print(c.radius)  # Uncommenting this line will raise an AttributeError

class Circle:
    def __init__(self, radius):
        self._radius = radius

    @property
    def radius(self):
        return self._radius

    @radius.setter
    def radius(self, value):
        if value < 0:
            raise ValueError("Radius cannot be negative")
        self._radius = value

    @property
    def area(self):
        import math
        return math.pi * self._radius ** 2

# Example usage:
c = Circle(5)
print(c.radius)  # Output: 5
print(c.area)    # Output: 78.53981633974483 (π * 5^2)

class Person:
    def __init__(self, first_name, last_name):
        self._first_name = first_name
        self._last_name = last_name

    @property
    def full_name(self):
        return f"{self._first_name} {self._last_name}"

# Example usage:
p = Person("John", "Doe")
print(p.full_name)  # Output: John Doe
# p.full_name = "Jane Doe"  # Uncommenting this line will raise an AttributeError

from dataclasses import dataclass

@dataclass
class Rectangle:
    length: float
    width: float

    @property
    def area(self):
        return self.length * self.width

# Example usage:
r = Rectangle(5, 3)
print(r.area)  # Output: 15