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#python #programming #developer #programmer #coding #coder #softwaredeveloper #computerscience #webdev #webdeveloper #webdevelopment #pythonprogramming #pythonquiz #ai #ml #machinelearning #datascience

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#python #programming #developer #programmer #coding #coder #softwaredeveloper #computerscience #webdev #webdeveloper #webdevelopment #pythonprogramming

https://t.iss.one/DataScienceQ

#python #programming #developer #programmer #coding #coder #softwaredeveloper #computerscience #webdev #webdeveloper #webdevelopment #pythonprogramming

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import numpy as np
numbers = np.array([1, 2, 3])
new_numbers = numbers + 1
print(new_numbers.tolist())

#python #programming #developer #programmer #coding #coder #softwaredeveloper #computerscience #webdev #webdeveloper #webdevelopment #pythonprogramming

https://t.iss.one/DataScienceQ

#python #programming #developer #programmer #coding #coder #softwaredeveloper #computerscience #webdev #webdeveloper #webdevelopment #pythonprogramming #pythonquiz #ai #ml #machinelearning #datascience

https://t.iss.one/DataScienceQ

#python #programming #developer #programmer #coding #coder #softwaredeveloper #computerscience #webdev #webdeveloper #webdevelopment #pythonprogramming

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# settings.py
INSTALLED_APPS = [
    # ... your apps
    'channels',
]

CHANNEL_LAYERS = {
    'default': {
        'BACKEND': 'channels.layers.RedisChannelLayer',
        'CONFIG': {
            "hosts": [('127.0.0.1', 6379)],
        },
    },
}

ASGI_APPLICATION = 'myproject.asgi.application'

# consumers.py
import json
from channels.generic.websocket import AsyncWebsocketConsumer
from channels.layers import get_channel_layer

class ChatConsumer(AsyncWebsocketConsumer):
    async def connect(self):
        self.room_name = self.scope['url_route']['kwargs']['room_name']
        self.room_group_name = f'chat_{self.room_name}'

        # Join room group
        await self.channel_layer.group_add(
            self.room_group_name,
            self.channel_name
        )

        await self.accept()

    async def disconnect(self, close_code):
        # Leave room group
        await self.channel_layer.group_discard(
            self.room_group_name,
            self.channel_name
        )

    # Receive message from WebSocket
    async def receive(self, text_data):
        text_data_json = json.loads(text_data)
        message = text_data_json['message']

        # Send message to room group
        await self.channel_layer.group_send(
            self.room_group_name,
            {
                'type': 'chat_message',
                'message': message
            }
        )

    # Receive message from room group
    async def chat_message(self, event):
        message = event['message']

        # Send message to WebSocket
        await self.send(text_data=json.dumps({
            'message': message
        }))

# routing.py
from django.urls import path
from channels.routing import ProtocolTypeRouter, URLRouter
from . import consumers

application = ProtocolTypeRouter({
    'websocket': URLRouter([
        path('ws/chat/<str:room_name>/', consumers.ChatConsumer.as_asgi()),
    ]),
})

# views.py (optional: trigger broadcast)
from channels.layers import get_channel_layer
from asgiref.sync import async_to_sync

def broadcast_message(room_name, message):
    channel_layer = get_channel_layer()
    async_to_sync(channel_layer.group_send)(
        f'chat_{room_name}',
        {
            'type': 'chat_message',
            'message': message
        }
    )

from your_app.models import Post, Comment # Assuming your models are here

Bad: This would cause N+1 queries if you loop and access comments

posts = Post.objects.all()

for post in posts:

    for comment in post.comment_set.all(): # database hit for EACH post

        print(comment.text)

Good: Fetches all posts AND all comments in just 2 queries!

posts_with_comments = Post.objects.prefetch_related('comment_set')

for post in posts_with_comments:
    print(f"Post: {post.title}")
    for comment in post.comment_set.all(): # 'comment_set' is the default related_name
        print(f"  - {comment.text}")

from django.db.models import Prefetch
from your_app.models import Post, Comment # Assuming Comment has 'is_approved' and 'created_at'

Define a custom queryset for only approved comments, ordered by creation

approved_comments_queryset = Comment.objects.filter(is_approved=True).order_by('-created_at')

Fetch posts and only their approved comments, storing them in a custom attribute

posts_with_approved_comments = Post.objects.prefetch_related(
    Prefetch('comment_set', queryset=approved_comments_queryset, to_attr='approved_comments')
)

for post in posts_with_approved_comments:
    print(f"Post: {post.title}")
    # Access them via the custom attribute 'approved_comments'
    for comment in post.approved_comments:
        print(f"  - (Approved) {comment.text}")

from your_app.models import Post, Comment # Assuming Comment has a ForeignKey to an Author model

posts_with_nested_relations = Post.objects.prefetch_related(
    # Here, we prefetch comments, and within the comments prefetch their authors
    Prefetch('comment_set', queryset=Comment.objects.select_related('author'))
)

for post in posts_with_nested_relations:
    print(f"\nPost: {post.title}")
    for comment in post.comment_set.all():
        print(f"  - {comment.text} by {comment.author.name}") # Access comment.author directly!