{"id":162,"date":"2024-01-25T14:05:14","date_gmt":"2024-01-25T14:05:14","guid":{"rendered":"https:\/\/learnpython.elegantwallp.com\/?p=162"},"modified":"2024-01-25T14:05:15","modified_gmt":"2024-01-25T14:05:15","slug":"python-__del__","status":"publish","type":"post","link":"https:\/\/learnpython.elegantwallp.com\/2024\/01\/25\/python-__del__\/","title":{"rendered":"Python __del__"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you will learn about the Python __del__<\/code> special method and understand how it works.<\/p>\n\n\n\n

Introduction to the Python __del__<\/code> method<\/h2>\n\n\n\n

In Python, the\u00a0garbage collector\u00a0manages memory automatically. The garbage collector will destroy the objects that are not\u00a0referenced.<\/p>\n\n\n\n

If an object implements the __del__<\/code> method, Python calls the __del__<\/code> method right before the garbage collector destroys the object.<\/p>\n\n\n\n

However, the garbage collector determines when to destroy the object. Therefore, it determines when the __del__<\/code> method will be called.<\/p>\n\n\n\n

The __del__<\/code> is sometimes referred to as a class finalizer. Note that __del__<\/code> is not the destructor because the garbage collector destroys the object, not the __del__<\/code> method.<\/p>\n\n\n\n

The Python __del__ pitfalls<\/h2>\n\n\n\n

Python calls the __del__<\/code> method when all object references are gone. And you cannot control it in most cases.<\/p>\n\n\n\n

Therefore, you should not use the __del__<\/code> method to clean up the resources. It\u2019s recommended to use the context manager.<\/p>\n\n\n\n

If the __del__<\/code> contains references to objects, the garbage collector will also destroy these objects when the __del__<\/code> is called.<\/p>\n\n\n\n

If the __del__<\/code> references the global objects, it may create unexpected behaviors.<\/p>\n\n\n\n

If an exception occurs inside the __del__<\/code> method, Python does not raise the exception but keeps it silent.<\/p>\n\n\n\n

Also, Python sends the exception message to the stderr. Therefore, the main program will be able to be aware of the exceptions during the finalization.<\/p>\n\n\n\n

In practice, you\u2019ll rarely use the __del__<\/code> method.<\/p>\n\n\n\n

Python __del__ example<\/h2>\n\n\n\n

The following defines a\u00a0Person<\/code>\u00a0class\u00a0with the special\u00a0__del__<\/code>\u00a0method, create a new instance of the\u00a0Person<\/code>, and set it to\u00a0None<\/code>:<\/p>\n\n\n\n

class Person: def __init__(self, name, age): self.name = name self.age = age def __del__(self): print('__del__ was called') if __name__ == '__main__': person = Person('John Doe', 23) person = None<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
__del__ was called<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
When we set the person<\/code> object to None<\/code>, the garbage collector destroys it because there is no reference. Therefore, the __del__<\/code> method was called.<\/p>\n\n\n\n
If you use the\u00a0del<\/code>\u00a0keyword to delete the\u00a0person<\/code>\u00a0object, the\u00a0__del__<\/code>\u00a0method is also called:<\/p>\n\n\n\n
person = Person('John Doe', 23) del person<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
__del__ was called<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
However, the del<\/code> statement doesn\u2019t cause a call to the __del__<\/code> method if the object has a reference.<\/p>\n","protected":false},"excerpt":{"rendered":"
Summary: in this tutorial, you will learn about the Python __del__ special method and understand how it works. Introduction to the Python __del__ method In Python, the\u00a0garbage collector\u00a0manages memory automatically. The garbage collector will destroy the objects that are not\u00a0referenced. If an object implements the __del__ method, Python calls the __del__ method right before the garbage collector destroys the object. However, the garbage […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[26],"tags":[],"class_list":["post-162","post","type-post","status-publish","format-standard","hentry","category-2-special-methods"],"_links":{"self":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts\/162","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/comments?post=162"}],"version-history":[{"count":1,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts\/162\/revisions"}],"predecessor-version":[{"id":163,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts\/162\/revisions\/163"}],"wp:attachment":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/media?parent=162"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/categories?post=162"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/tags?post=162"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}