My Python class defines the __del__ method, but it is not called when I delete the object

__del__ is a magic method in Python. These magical methods allow us to implement some very neat tricks in object-oriented programming. They are also called Dunder methods. These methods are identified by two underscores (__) used as prefix and suffix.

In Python, we use __new__() to create an object and use __init__() to initialize it. However, to destroy an object we have __del__().

Example

Let's create and delete an object -

class Demo:
   def __init__(self):
      print("We are creating an object.");
   # destructor
   def __del__(self):
      print("We are deleting an object.");

# Createing and deleting an object
ob = Demo();
del ob;

Output

We are creating an object.
We are deleting an object.

reason

However, if a class defines __del__ but does not call it when deleting the object, there may be many reasons -

• The del statement does not necessarily call __del__() - it simply decrements the object's reference count and calls __del__() if it reaches zero.

• __del__() method can be called randomly. - If your data structure contains circular links, the reference count will never get back to zero. Python runs an algorithm to detect such cycles, but the garbage collector may run some time after the last reference to the data structure disappears.

Solve the problem

Here are the fixes -

• Don't call __del__() directly - _del__() should call close(), and close() should ensure that it can be called multiple times on the same object.

• Avoid circular references - Use the weakref module to avoid circular references. It allows you to point to an object without increasing its reference count. The Weakref module can also be used to obtain instances of classes

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