Using Python's property() to Create Managed Attributes

The property() function returns a managed attribute for new‑style classes, allowing controlled access to an object's data.

Syntax :

class property([fget[, fset[, fdel[, doc]]]])

Parameters :

fget – function that gets the attribute value

fset – function that sets the attribute value

fdel – function that deletes the attribute

doc – optional docstring for the attribute

The function returns a new‑style class property.

Example 1 – Explicit getter, setter, deleter :

class C(object):
    def __init__(self):
        self._x = None
    def getx(self):
        return self._x
    def setx(self, value):
        self._x = value
    def delx(self):
        del self._x
    x = property(getx, setx, delx, "I'm the 'x' property.")

c = C()
# c.x triggers getter, c.x = value triggers setter, del c.x triggers deleter

If a doc argument is supplied, it becomes the property's docstring; otherwise the docstring of fget is copied.

Example 2 – Using @property decorator for a read‑only attribute :

class Parrot(object):
    def __init__(self):
        self._voltage = 100000
    @property
    def voltage(self):
        """Get the current voltage."""
        return self._voltage

# voltage() is now accessible as a read‑only attribute

The same decorator can be combined with .setter and .deleter to define writable properties:

class C(object):
    def __init__(self):
        self._x = None
    @property
    def x(self):
        """I'm the 'x' property."""
        return self._x
    @x.setter
    def x(self, value):
        self._x = value
    @x.deleter
    def x(self):
        del self._x

Example 3 – Custom class with property created via function call :

class ceshi():
    def __init__(self, size=10):
        self.size = size
    def getSize(self):
        return self.size
    def setSize(self, value):
        self.size = value
    def delSize(self):
        del self.size
    x = property(getSize, setSize, delSize)

sx = ceshi(100)
print(sx.x)      # getter
sx.x = 106        # setter
print(sx.x)
print(del sx.x)  # deleter raises AttributeError

Additional built‑in functions for attribute manipulation include hasattr() , getattr() , setattr() , and delattr() , which respectively test for existence, retrieve, assign, and delete attributes on objects.