THEORY AND PRACTICE

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While Loop

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Tasks

Занятие 5. While cycle

Difficulty level:

Task«The long -awaited vacation»

Anna dreams of vacation and wants to accumulate a certain amount for it. She starts with a certain annual salary and plans her savings. Each year, its employer promises an increase, and her salary increases by 15% compared to the previous year. Anna is very disciplined and decides to save exactly 10% of her annual salary at the end of each year.

additional condition: after the output of the main result (the number of years), the program should ask the user, does it want to see it, he wants to see it A detailed report by year. If the user introduces yes, the program must withdraw his number for each year, the salary for this year, how much was delayed and what total amount of accumulations became at the end of the year.

& nbsp;

Input format

Anna's annual salary (number, & nbsp; float )
(Number, & nbsp; float
str

Output format

str )
str )

Example

Input

100000
50000
Yes

Output

Anna will take 5 years to save on vacation.
Want to see a detailed annual report? (yes/no): & nbsp;
--- Annual report ---
year 1: salary 100,000.00, it was postponed 10,000.00, a total of 10,000.00
year 2: salary 115000.00, laid out 11500.00, total accumulated 21500.00
year 3: salary 132250.00, laid out 13225.00, total of a total Accumulated 34725.00
year 4: salary 152087.50, postponed 15208.75, total accumulated 49933.75
year 5: salary 174900.62, set aside 17490.06, total accumulated 67423.81

Hint

While in python

In the Python programming language, the while loop construction can have an optional else block. This block is executed only when the loop completes in its natural way, that is, when its condition becomes false, and not as a result of a forced interruption using the break operator.

Syntax:

while condition:
    # the body of the loop
    # ...the code that runs on each iteration...
else:
    # else block
    # ...the code that is executed if the loop ended without a break...

You can think of the else block as a "plan B": it is triggered if the main goal within the loop (which is usually completed through a break) has not been achieved.

Usage example: Searching for an element

Consider a classic problem where we search for a number in a list. If a number is found, we immediately break the loop using break. If we have checked all the elements and still haven't found what we are looking for, the else block is executed.

numbers = [1, 2, 3, 4, 5]
target = 8 # Let's try to find a number that is not in the list.

index = 0
while index < len(numbers):
    if numbers[index] == target:
        print(f"Success! {target} found at {index}.")
break # Goal reached, exit the loop
    index += 1
else:
    # This block will be executed because break was not called
    print(f"The search is completed. {target} not found in the list.")

How it works:

The whileloop is executed as long as the index < len(numbers) condition is true.
Inside the loop, we check whether the current element is equal to the desired one (target).
If we find a value, a success message is displayed and the loop is immediately interrupted by the break statement. The else block is ignored in this case.
If the loop reaches the end (checked all the elements), it means that break has never worked. The index < len(numbers) condition becomes false, and then the else block is executed, reporting a failed search.

A useful tip: Using while...else helps to avoid "flagged" variables. Without this block, the code would look like this:

# Alternative version with "flag"
numbers = [1, 2, 3, 4, 5]
target = 8
found = False # Flag variable

index = 0
while index < len(numbers):
    if numbers[index] == target:
        found = True
        break
    index += 1

if found:
    print(f"Success! {target} found.")
else:
print(f"Search completed. {target} not found in the list.")

As you can see, the while...else construction makes the code cleaner, more concise, and more "Pythonic", eliminating the need to manually control the flag.

If `break` is missing

If there is no break operator in the body of the while loop, then the else block will always be executed after the loop ends.

count = 0
while count < 3:
print(f"Iteration number {count}")
count += 1
else:
print("The loop ended naturally, so the else block is executed.")

Here, the while loop runs until count is less than 3. As soon as count becomes 3, the loop condition becomes false, and control is transferred to the else block.

Important nuances

What about continue? The continue operator does not interrupt the loop, but only ends the current iteration ahead of schedule. It does not affect the execution of the else block in any way.
If the loop was never executed? If the while condition is initially false, the loop body will not be executed even once. However, the else block will still run, since the loop ended "normally" (it was not interrupted via break).

value = 10
while value < 5: # The condition is immediately false
    print("This text will never be printed")
else:
print("The cycle didn't even start, but it ended normally, so else worked.")

This also works for for loops! The same logic applies to for...else loops. The else block after for is executed if the cycle has passed through all the elements and has not been interrupted using break.

Output

The while...else construction is a powerful and elegant Python tool. It is ideal for situations where you need to perform an action only if the loop has completed its work completely without being interrupted. This is especially useful in search algorithms, condition checking, or when working with data streams, where break signals a special event, and else indicates a regular termination without any.

main.py

Test 1

Test 2

Test 3

Test 4

Test 5

Test 6

Test 7

Test 8

Test 9

Test 10

Developer’s solution

# Запрашиваем у пользователя начальные данные
initial_salary = float(input())
vacation_cost = float(input())

# Проверяем корректность введенных данных
if initial_salary <= 0 or vacation_cost <= 0:
    print("Ошибка: Зарплата и стоимость отпуска должны быть положительными числами.")
else:
    # Инициализация переменных для цикла
    current_salary = initial_salary  # Текущая годовая зарплата
    total_savings = 0.0              # Общая сумма накоплений
    years = 0                        # Счетчик лет
    
    # Список для хранения детальной информации по годам
    yearly_details = []

    # Цикл while работает, пока накопленная сумма меньше стоимости отпуска
    while total_savings < vacation_cost:
        years += 1  # Увеличиваем счетчик лет на 1
        
        # Рассчитываем, сколько денег будет отложено в этом году (10%)
        saved_this_year = current_salary * 0.10
        
        # Добавляем отложенные деньги к общей сумме накоплений
        total_savings += saved_this_year
        
        # Сохраняем детали этого года для возможного отчета
        yearly_details.append((years, current_salary, saved_this_year, total_savings))
        
        # Увеличиваем зарплату на 15% для следующего года
        current_salary *= 1.15

    # Выводим основной результат
    print(f"Анне потребуется {years} лет, чтобы накопить на отпуск.")
    
    # Спрашиваем пользователя, нужен ли детальный отчет
    show_details = input("Хотите увидеть подробный годовой отчет? (да/нет): ")
    
    # Условие для вывода детального отчета
    if show_details.lower() == 'да':
        print("\n--- Годовой отчет ---")
        # Цикл for для вывода информации по каждому году
        for detail in yearly_details:
            year, salary, saved, total = detail
            # Выводим отформатированную строку с данными за год
            print(f"Год {year}: Зарплата {salary:.2f}, Отложено {saved:.2f}, Всего накоплено {total:.2f}")

🎉 Congratulations! 🎉

You did an excellent job with the task! It was a challenging problem, but you found the correct solution. You are one step closer to mastering programming! Keep up the good work, because every stage you pass makes you even stronger.

THEORY AND PRACTICE

Занятие 5. While cycle

Difficulty level:

Task«The long -awaited vacation»

Input format

Output format

Example

Input

Output

Hint

While in python

Usage example: Searching for an element

If break is missing

Important nuances

Output

Помощник ИИ

If `break` is missing