Python & Django: Writing Code That Scales, Not Just Code That Works

Many developers learn Python and Django by building CRUD applications. That's a great start.

But as projects grow, the challenge changes:

❌ It's no longer about making the feature work.

✅ It's about making the feature maintainable, scalable, secure, and efficient.

The difference between a junior and a mid-level developer is often not the syntax they know, but the engineering decisions they make.

1. Don't Query the Database More Than Necessary

A common mistake in Django is creating N+1 query problems.

Bad Example
orders = Order.objects.all()

for order in orders:
print(order.customer.name)

If there are 100 orders, Django may execute 101 queries.

Better Approach
orders = Order.objects.select_related('customer')

for order in orders:
print(order.customer.name)

Now Django performs a JOIN and retrieves everything in a single query.

Why It Matters
Faster response times
Reduced database load
Better scalability

Performance optimization often starts with understanding your queries.

1. Keep Business Logic Out of Views

Many developers write everything inside views.

Bad Example
def create_order(request):
customer = Customer.objects.get(id=request.POST['customer_id'])

order = Order.objects.create(
    customer=customer,
    total=calculate_total(customer)
)

send_order_email(order)

return JsonResponse({"status": "success"})

The view now handles:

Validation
Business rules
Database operations
Notifications

This becomes difficult to maintain.

Better Structure

services/order_service.py

class OrderService:

@staticmethod
def create_order(customer):
    order = Order.objects.create(
        customer=customer,
        total=calculate_total(customer)
    )

    send_order_email(order)

    return order

views.py

def create_order(request):
customer = Customer.objects.get(
id=request.POST['customer_id']
)

order = OrderService.create_order(customer)

return JsonResponse({"status": "success"})

Benefits:

Cleaner code
Easier testing
Better separation of concerns

1. Use Django ORM Efficiently

Instead of processing large datasets in Python, let the database do the work.

Less Efficient
orders = Order.objects.all()

total = sum(order.amount for order in orders)
Better
from django.db.models import Sum

total = Order.objects.aggregate(
total_amount=Sum('amount')
)

Databases are optimized for aggregation.

Use them.

1. Use Model Methods for Domain Logic Instead of if order.status == "paid": print("Order completed")

Scattered everywhere.

Encapsulate Logic
class Order(models.Model):
status = models.CharField(max_length=20)

def is_completed(self):
    return self.status == "paid"

Usage:

if order.is_completed():
print("Order completed")

Your code becomes more expressive and easier to maintain.

1. Use Environment Variables

Never hardcode secrets.

Bad
SECRET_KEY = "my-secret-key"
Better
import os

SECRET_KEY = os.getenv("SECRET_KEY")

Store secrets in:

SECRET_KEY=super-secret-value
DATABASE_URL=postgresql://...

Security is not optional in production.

1. Leverage Python Features

Many developers use Python like other languages and miss its power.

List Comprehension
numbers = [1, 2, 3, 4, 5]

squares = [n * n for n in numbers]

Result:

[1, 4, 9, 16, 25]

Cleaner and more readable.

Dictionary Comprehension
users = ["john", "alice", "bob"]

data = {
user: len(user)
for user in users
}

Output:

{
"john": 4,
"alice": 5,
"bob": 3
}

1. Write Code for Future Developers

Ask yourself:

"Can another developer understand this code six months from now?"

Good code is not clever.

Good code is:

Readable
Predictable
Testable
Maintainable
Example of Clean Django Code
class Order(models.Model):
customer = models.ForeignKey(
Customer,
on_delete=models.CASCADE
)
amount = models.DecimalField(
max_digits=10,
decimal_places=2
)
status = models.CharField(
max_length=20
)

def mark_as_paid(self):
    self.status = "paid"
    self.save()

Usage:

order = Order.objects.get(id=1)

order.mark_as_paid()

Simple.

Readable.

Maintainable.

Final Thought

A professional Python/Django developer doesn't focus on writing more code.

They focus on writing:

✔ Cleaner code
✔ Faster code
✔ Safer code
✔ Scalable code
✔ Maintainable code

Because in real-world software development, code is read far more often than it is written.

Write code that your future self - and your team - will thank you

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Comments

[Jun Hao]

I want to get the stable ... through collaboration with u

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tahnk you for seeing my post

best regards