Pass by reference vs value in Python

number before= 6

in function value updated to 12

after function num value= 6

list before ['E']

in function list updated to ['E', 'D']

after function list is ['E', 'D']

In the above code, we have shown how Python uses call by reference object concept in its program. We pass an integer in function call_by_value().

Integers are immutable objects hence Python works according to call by value, and the changes made in the function are not reflected outside the function.

We then pass list to function by reference. In function call_by_reference() we pass a list that is an mutable object. Python works according to call by reference in this function and the changes made inside the function can also be seen outside the function.

Comments

Implementing Advance Query Optimization in Django ORM

Django's ORM makes database interactions seamless, allowing developers to write queries in Python without raw SQL. However, as applications scale, inefficient queries can slow down performance, leading to high latency and database load. This guide explores advanced query optimization techniques in Django ORM to go beyond basic CRUD (Create, Read, Update, Delete) operations and improve efficiency. 1. Use QuerySet Caching to Avoid Repeated Queries Using cache reduces redundant queries for frequently accessed data. Caching helps reduce repeated database hits. 2. Avoid .count() on Large Datasets Using .count() on large tables can be expensive Inefficient way: Optimized way ( .exists() is Faster) 3. Use Indexes for Faster Lookups Indexes speed up queries on frequently filtered fields. Add db_index=True for frequently queried fields: 4. Optimize Bulk Inserts and Updated Performing operations on multiple records one by one is inefficient. Use bulk_create() for mass insert...

Django pk vs id

Django pk VS id If you don’t specify primary_key=True for any fields in your model, Django will automatically add an IntegerField to hold the primary key, so you don’t need to set primary_key=True on any of your fields unless you want to override the default primary-key behavior. The primary key field is read-only. If you change the value of the primary key on an existing object and then save it, a new object will be created alongside the old one Example: class UserProfile ( models . Model ): name = models . CharField ( max_length = 500 ) email = models . EmailField ( primary_key = True ) def __str__ ( self ): return self . name suppose we have this model. In this model we have make email field as primary key. now django default primary key id field will be gone. It'll remove from database. we can not query as UserProfile.objects.get(id=1) after make email as primary key this query will throw an error. Now we have to use pk Us...

Django select_related and prefetch_related

Difference between select_related and prefetch_related Reducing SQL queries is one of the first steps when optimizing a Django project. There are two powerful methods included in the Django ORM to help us that can boost performance by creating a single more complex QuerySet rather than multiple, smaller queries. In this project we will understand about select_related and prefetch_related. Django use these two orm method to reduce sql queries in database based on different scenario. select_related Lets assume this two model we have. class Author ( models . Model ): name = models . CharField ( max_length = 200 ) def __str__ ( self ): return self . name class Courses ( models . Model ): name = models . CharField ( max_length = 200 ) author = models . ForeignKey ( Author , on_delete = models . CASCADE , related_name = 'courses' ) def __str__ ( self ): return self . name Here we have two mode. ...

Django Interview Preparation

Search This Blog