Summary  
This chapter demonstrates how to use `break` (and `continue`) within nested loops to exit an inner loop when a condition is met while allowing the outer loop to proceed.

General domain of usage  
Travel expense processing

Let's apply the concepts of `break` and `continue` to analyze travel costs practically. We'll combine a `while` loop and a `for` loop to process expenses across multiple trips.

Imagine you have multiple trips, and each trip has a list of expenses. If any expense exceeds a specific budget threshold, we will stop processing that trip immediately.

# List of trips with their respective expenses
travel_costs = [
    [100, 150, 300, 50],   # Trip 1
    [200, 500, 100, 80],   # Trip 2
    [120, 180, 400, 150]   # Trip 3
]

# Budget threshold
budget = 200

# Outer while loop to iterate through trips
i = 0
while i < len(travel_costs):
    print(f"Processing expenses for Trip {i + 1}:")
    
    # Inner for loop to iterate through expenses
    for cost in travel_costs[i]:
        # If expense exceeds the budget
        if cost > budget:  
            print('Expense', cost, 'exceeds the budget. Stopping this trip.')
            break
        print('Expense:', cost)
    
    i += 1  # Move to the next trip
    print('')  # Add a new line for readability

- **Outer loop**: iterates through the list of trips using the index `i`;
- **Inner loop**: processes each expense in the current trip;
- `break` **in the inner loop**:
if an expense exceeds the `budget`, the `break` statement stops processing expenses for the current trip.

import unittest
import importlib

def _dynamic_test(test_case, condition, success_message, failure_message):
    if condition:
        test_case._testMethodName = success_message
        test_case.assertTrue(True, success_message)
    else:
        test_case._testMethodName = failure_message
        test_case.fail(failure_message)

class TestUserCode(unittest.TestCase):

    def test_significant_expenses_is_declared(self):
        try:
            user_code = importlib.import_module("user_code")
            _ = user_code.significant_expenses
            _dynamic_test(self, True, "The `significant_expenses` list is declared.", "")
        except AttributeError:
            _dynamic_test(self, False, "", "Expected `significant_expenses` to be declared.")
        except ImportError as e:
            self.fail(f"Failed to import module: {e}")

    def test_significant_expenses_correct_values(self):
        try:
            user_code = importlib.import_module("user_code")
            expected_expenses = [
                next((cost for cost in trip if cost > 200), None)
                for trip in user_code.travel_costs
            ]
            _dynamic_test(
                self,
                user_code.significant_expenses == expected_expenses,
                "The `significant_expenses` list contains correctly identified values.",
                f"Expected `significant_expenses` to be `{expected_expenses}`, but got `{user_code.significant_expenses}`."
            )
        except AttributeError:
            _dynamic_test(self, False, "", "Expected `significant_expenses` to be declared.")
        except ImportError as e:
            self.fail(f"Failed to import module: {e}")

if __name__ == "__main__":
    unittest.main()

test_main.py

Build confidence in mastering Python loops! Start with the basics of for and while loops and progress to advanced concepts like nested loops, control statements, and dynamic conditions. With hands-on practice and real-world examples, gain the skills to write efficient, clean, and powerful code. Perfect for beginners and anyone looking to sharpen their Python expertise!

Master how to iterate through sequences with for loop, use range() effectively, explore conditions with if/else, and control loops with break and continue. Get ready to write efficient, clean, and practical code as you tackle fun challenges!

break/continue in a Nested Loop

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