I'm working on a Python application and running into an issue with Python optimization. Here's the problematic code:

# Current implementation
class DataProcessor:
    def __init__(self):
        self.data = []
    
    def process_large_file(self, filename):
        with open(filename, 'r') as f:
            self.data = f.readlines()  # Memory issue with large files
        return self.process_data()

The error message I'm getting is: "KeyError: 'missing_key'"

What I've tried so far:

• Used pdb debugger to step through the code
• Added logging statements to trace execution
• Checked Python documentation and PEPs
• Tested with different Python versions
• Reviewed similar issues on GitHub and Stack Overflow

Environment information:

• Python version: 3.11.0
• Operating system: Ubuntu 22.04
• Virtual environment: venv (activated)
• Relevant packages: django, djangorestframework, celery, redis

Any insights or alternative approaches would be very helpful. Thanks!

To handle Django database transactions properly and avoid data inconsistency, use Django's transaction management:

from django.db import transaction

# Method 1: Decorator
@transaction.atomic
def transfer_money(from_account, to_account, amount):
    from_account.balance -= amount
    from_account.save()
    
    to_account.balance += amount
    to_account.save()

# Method 2: Context manager
def complex_operation():
    with transaction.atomic():
        # All operations in this block are atomic
        user = User.objects.create(username='test')
        profile = UserProfile.objects.create(user=user)
        # If any operation fails, all are rolled back

For more complex scenarios with savepoints:

def nested_transactions():
    with transaction.atomic():
        # Outer transaction
        user = User.objects.create(username='test')
        
        try:
            with transaction.atomic():
                # Inner transaction (savepoint)
                risky_operation()
        except Exception:
            # Inner transaction rolled back, outer continues
            handle_error()

The RecursionError occurs when Python's recursion limit is exceeded. Here are several solutions:

1. Increase recursion limit (temporary fix):

import sys
sys.setrecursionlimit(10000)  # Default is usually 1000

2. Convert to iterative approach (recommended):

# Recursive (problematic for large inputs)
def factorial_recursive(n):
    if n <= 1:
        return 1
    return n * factorial_recursive(n - 1)

# Iterative (better)
def factorial_iterative(n):
    result = 1
    for i in range(2, n + 1):
        result *= i
    return result

3. Use memoization for recursive algorithms:

from functools import lru_cache

@lru_cache(maxsize=None)
def fibonacci(n):
    if n < 2:
        return n
    return fibonacci(n-1) + fibonacci(n-2)

4. Tail recursion optimization (manual):

def factorial_tail_recursive(n, accumulator=1):
    if n <= 1:
        return accumulator
    return factorial_tail_recursive(n - 1, n * accumulator)

The choice between Django signals and overriding save() depends on your use case:

Use save() method when:

• The logic is directly related to the model
• You need to modify the instance before saving
• The operation is essential for data integrity

class Article(models.Model):
    title = models.CharField(max_length=200)
    slug = models.SlugField(unique=True)
    
    def save(self, *args, **kwargs):
        if not self.slug:
            self.slug = slugify(self.title)
        super().save(*args, **kwargs)

Use signals when:

• You need decoupled logic
• Multiple models need the same behavior
• You're working with third-party models

from django.db.models.signals import post_save
from django.dispatch import receiver

@receiver(post_save, sender=User)
def create_user_profile(sender, instance, created, **kwargs):
    if created:
        UserProfile.objects.create(user=instance)

This Django error typically occurs when you're trying to save a model instance that violates a unique constraint. Here's how to handle it properly:

from django.db import IntegrityError
from django.http import JsonResponse

try:
    user = User.objects.create(
        username=username,
        email=email
    )
except IntegrityError as e:
    if 'username' in str(e):
        return JsonResponse({'error': 'Username already exists'}, status=400)
    elif 'email' in str(e):
        return JsonResponse({'error': 'Email already exists'}, status=400)
    else:
        return JsonResponse({'error': 'Data integrity error'}, status=400)

Always use get_or_create() when you want to avoid duplicates:

user, created = User.objects.get_or_create(
    username=username,
    defaults={'email': email, 'first_name': first_name}
)