The property() function in Python is used to create and return a property object. It allows defining a method as a getter, setter or a deleter of an attribute.

Syntax:

property(fget=None, fset=None, fdel=None, doc=None)  

Parameters:
- fget: Optional. A method to get the value of the attribute.
- fset: Optional. A method to set the value of the attribute.
- fdel: Optional. A method to delete the attribute.
- doc: Optional. A string to provide the documentation for the attribute.

Return value:
- A property object that can be assigned to a class attribute. When accessed, the methods defined by fget, fset, and fdel will be called accordingly.

Example usage:

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:  
            self._radius = value  
        else:  
            raise ValueError("Radius cannot be negative!")  
    @radius.deleter  
    def radius(self):  
        del self._radius  
# Creating an instance of Circle  
c = Circle(5)  
# Accessing the radius attribute using the property  
print(c.radius)  # Output: 5  
# Setting a new value to the radius attribute  
c.radius = 10  
print(c.radius)  # Output: 10  
# Trying to set a negative value to the radius attribute  
c.radius = -5  # Raises a ValueError  
# Deleting the radius attribute  
del c.radius  
print(c.radius)  # AttributeError: 'Circle' object has no attribute '_radius'  

In the above example, @property decorator is used to define a getter method for the radius attribute, @radius.setter decorator is used to define a setter method, and @radius.deleter decorator is used to define a deleter method.