Python : __delete__ vs __del__

Both __delete__ and __del__ are dunder or magic methods in Python. Dunder or magic methods in Python are the methods having two prefix and suffix underscores in the method name. Dunder here means “Double Under (Underscores)”. These are commonly used for operator overloading.

__del__

__del__ is a destructor method which is called as soon as all references of the object are deleted i.e when an object is garbage collected.

Syntax:

def __del__(self):
    body of destructor
    .
    .

Example: Here is the simple example of destructor. By using del keyword we deleted the all references of object ‘obj’, therefore destructor invoked automatically.

# Python program to demonstrate
# __del__


class Example:

    # Initializing
    def __init__(self):
        print("Example Instance.")

    # Calling destructor
    def __del__(self):
        print("Destructor called, Example deleted.")

obj = Example()
del obj

Output:

Example Instance.
Destructor called, Example deleted.

Note : The destructor was called after the program ended or when all the references to object are deleted i.e when the reference count becomes zero, not when object went out of scope.

__delete__

__delete__ is used to delete the attribute of an instance i.e removing the value of attribute present in the owner class for an instance.

Note: This method only deletes the attribute which is a descriptor.

Syntax:

def __delete__(self, instance):
    body of delete
    .
    .

Example:

# Python program to demonstrate
# __delete__


class Example(object):

    # Initializing
    def __init__(self):
        print("Example Instance.")

    # Calling __delete__
    def __delete__(self, instance):
        print ("Deleted in Example object.")


# Creating object of Example
# class as an descriptor attribute
# of this class
class Foo(object):
    exp = Example()

# Driver's code
f = Foo()
del f.exp

Output:

Example Instance.
Deleted in Example object.

Difference between __delete and __del__

Example: A combine example of __del__ and __delete__.

# Python program to demonstrate
# __del__ and __delete__


class Example(object):

    # Initializing
    def __init__(self):
        self.value = ''

    # deletes an attribute
    def __delete__(self, instance):
        print ("Inside __delete__")

    # Destructor
    def __del__(self):
        print("Inside __del__")


class Foo(object):
    exp = Example()

# Driver's code
f = Foo()
del f.exp

Output:

Inside __delete__
Inside __del__