Refactoring restructures existing code to improve design and maintainability without changing its externally observable behavior. It removes repetition, clarifies responsibilities, and keeps code easier to change; it does not add features. section 2.1.4 section 9.0
Look for these practical signals and opportunities:
- Repeated code often violates the DRY principle; extract the shared portion so changes happen in one place. section 1.1.2 section 2.1.4
- When a class grows beyond one purpose, separate its mixed responsibilities into distinct classes. section 9.6
- When tests repeat setup work, move the shared operation into unittest.TestCase.setUp. section 13.3.3
Extracting repeated formatting
Repeated format specifications make later changes inconvenient and error-prone. Extract the format into a parameterized function: def create_formatted_records(fmt): for i in range(3): task_id = task_ids[i] name = task_names[i] urgency = task_urgencies[i] print(f'{task_id:{fmt}}{name:{fmt}}{urgency:{fmt}}') Calling create_formatted_records('^15') or create_formatted_records('^18') changes the layout in one place while preserving the records and function’s purpose. section 2.1.4
Listing 13.7 Overriding the setUp method (test_task_func.py)
from task_func import Task, create_task, create_task_from_dict
import unittest
class TestTaskCreation(unittest.TestCase):
def setUp(self):
task_to_compare = Task("Laundry", 3)
self.task_dict = task_to_compare.__dict__
def test_create_task(self):
task_text = "Laundry,3"
created_task = create_task(task_text)
self.assertEqual(created_task.__dict__, self.task_dict)
def test_create_task_from_dict(self):
task_data = {"title": "Laundry", "urgency": 3}
created_task = create_task_from_dict(task_data)
self.assertEqual(created_task.__dict__, self.task_dict)
if __name__ == "__main__":
unittest.main()
Shows a unittest setup refactoring that creates one comparison object before each test instead of duplicating it inside multiple test methods. section 13.3.3
