Views

# courses/views.py
from django.shortcuts import render, get_object_or_404
from django.http import JsonResponse, HttpResponse
from .models import Course

def course_list(request):
    """List all live courses."""
    courses = Course.objects.filter(is_live=True).select_related("category")
    return render(request, "courses/list.html", {"courses": courses})

def course_detail(request, slug):
    """Show one course by slug."""
    # get_object_or_404 — raises 404 instead of DoesNotExist error
    course = get_object_or_404(Course, slug=slug, is_live=True)
    return render(request, "courses/detail.html", {"course": course})

# API view — return JSON instead of HTML
def course_api(request):
    courses = Course.objects.filter(is_live=True).values(
        "id", "title", "slug", "level"
    )
    return JsonResponse({"courses": list(courses)})

# Django's ORM translates Python to SQL automatically

# Get all courses
Course.objects.all()

# Filter
Course.objects.filter(is_live=True)
Course.objects.filter(level="beginner", is_live=True)
Course.objects.filter(title__icontains="python")  # case-insensitive
Course.objects.filter(created_at__year=2025)
Course.objects.exclude(is_live=False)

# Ordering
Course.objects.order_by("-created_at")  # - means descending
Course.objects.order_by("title", "-created_at")

# Limit
Course.objects.all()[:10]  # first 10
Course.objects.all()[10:20]  # next 10 (pagination)

# Single object
Course.objects.get(id=42)         # raises DoesNotExist or MultipleObjects
Course.objects.get(slug="nextjs")

# Aggregation
from django.db.models import Count, Avg
Course.objects.aggregate(total=Count("id"))  # {"total": 12}

# Create, update, delete
course = Course.objects.create(title="Flask", slug="flask")
course.title = "Flask Framework"
course.save()
Course.objects.filter(is_live=False).update(is_live=True)
Course.objects.filter(id=99).delete()