Designing Django Models: Transactions & Categories for Finance Apps

from django.db import models

class Category(models.Model):
    name = models.CharField(max_length=50, unique=True)
    def __str__(self):
        return self.name

class Transaction(models.Model):
    INCOME = 'IN'
    EXPENSE = 'EX'
    TRANSACTION_TYPES = [
        (INCOME, 'Income'),
        (EXPENSE, 'Expense'),
    ]
    category = models.ForeignKey(Category, on_delete=models.CASCADE)
    amount = models.DecimalField(max_digits=10, decimal_places=2)
    date = models.DateField()
    transaction_type = models.CharField(max_length=2, choices=TRANSACTION_TYPES)
    notes = models.TextField(blank=True)
    def __str__(self):
        return f"{self.get_transaction_type_display()} - {self.category.name}: {self.amount} on {self.date}"