"""
Урок 19. Summary Session 5 — весь код примеров одним файлом.

Источник: subjects/python-fundamentals/course/lessons/19-summary-session-5/examples.html
Файл собран автоматически (tools/build_lesson_examples.py): правьте страницу урока.
Запуск: python lesson-19.py
"""



# ====================================================================
# Пример 1. Перебор строки
# ====================================================================
text = "Python"
for letter in text:
    print(letter)
# P
# y
# t
# h
# o
# n


# ====================================================================
# Пример 2. Разные варианты range
# ====================================================================
print("range(5):")
for i in range(5):
    print(i, end=" ")
print()

print("range(2, 6):")
for i in range(2, 6):
    print(i, end=" ")
print()

print("range(1, 10, 2):")
for i in range(1, 10, 2):
    print(i, end=" ")
print()

print("range(10, 0, -2):")
for i in range(10, 0, -2):
    print(i, end=" ")
print()
# range(5):
# 0 1 2 3 4
# range(2, 6):
# 2 3 4 5
# range(1, 10, 2):
# 1 3 5 7 9
# range(10, 0, -2):
# 10 8 6 4 2


# ====================================================================
# Пример 3. break, continue, else
# ====================================================================
for letter in "Python":
    if letter == "h":
        break
    print(letter, end=" ")
else:
    print("Буква h не найдена")
print()

for letter in "Python":
    if letter == "h":
        continue
    print(letter, end=" ")
print()

for letter in "abc":
    if letter == "z":
        break
    print(letter, end=" ")
else:
    print("- цикл прошёл без break")
# P y t
# P y t o n
# a b c - цикл прошёл без break


# ====================================================================
# Пример 4. Вложенные циклы
# ====================================================================
words = ["cat", "dog", "bird"]
for word in words:
    print(f"Word: {word}")
    for letter in word:
        print(letter, end=" ")
    print()


# ====================================================================
# Пример 5. Создание списков и срезы
# ====================================================================
empty = []
also_empty = list()
chars = list("python")
values = list(range(0, 10, 2))
print(empty, also_empty, chars, values)

numbers = [0, 1, 2, 3, 4, 5, 6]
print(numbers[1:4])    # [1, 2, 3]
print(numbers[::2])    # [0, 2, 4, 6]
print(numbers[::-1])   # [6, 5, 4, 3, 2, 1, 0]
print(numbers[-4:-1])  # [3, 4, 5]
# [] [] ['p', 'y', 't', 'h', 'o', 'n'] [0, 2, 4, 6, 8]
# [1, 2, 3]
# [0, 2, 4, 6]
# [6, 5, 4, 3, 2, 1, 0]
# [3, 4, 5]


# ====================================================================
# Пример 6. Изменение списка: по индексу и по срезу
# ====================================================================
items = ["apple", "banana", "cherry"]
items[1] = "blueberry"
print(items)  # ['apple', 'blueberry', 'cherry']

numbers = [10, 20, 30, 40, 50]
numbers[1:3] = [200, 300]
print(numbers)  # [10, 200, 300, 40, 50]


# ====================================================================
# Пример 7. Операции со списками
# ====================================================================
list1 = [1, 2, 3]
list2 = [4, 5, 6]
print(list1 + list2)  # [1, 2, 3, 4, 5, 6]

print([0] * 5)        # [0, 0, 0, 0, 0]

numbers = [1, 2, 3, 4, 5]
print(3 in numbers)   # True
print(6 in numbers)   # False
print(len(numbers))   # 5


# ====================================================================
# Пример 8. Чётные и нечётные числа в диапазоне
# ====================================================================
start = 1  # результат int(input("Введите начало диапазона: "))
end = 10  # результат int(input("Введите конец диапазона: "))

even = []
odd = []
for number in range(start, end + 1):
    if number % 2 == 0:
        even.append(number)
    else:
        odd.append(number)

print("Четные:", *even)
print("Нечетные:", *odd)
# Четные: 2 4 6 8 10
# Нечетные: 1 3 5 7 9


# ====================================================================
# Пример 9. enumerate(): индекс и значение вместе
# ====================================================================
fruits = ["apple", "banana", "cherry"]
for index, fruit in enumerate(fruits):
    print(f"{index}: {fruit}")
# 0: apple
# 1: banana
# 2: cherry


# ====================================================================
# Пример 10. List comprehension: короткая запись фильтра
# ====================================================================
numbers = [1, 2, 3, 4, 5, 6]
even_numbers = [n for n in numbers if n % 2 == 0]
print(even_numbers)  # [2, 4, 6]

# то же самое обычным циклом
even_numbers_loop = []
for n in numbers:
    if n % 2 == 0:
        even_numbers_loop.append(n)
print(even_numbers_loop == even_numbers)  # True


# ====================================================================
# Пример 11. Изменяемость: список можно менять, строку — нет
# ====================================================================
numbers = [1, 2, 3]
numbers[0] = 100
print(numbers)  # [100, 2, 3]

text = "hello"
try:
    text[0] = "H"
except TypeError as error:
    print(f"Ошибка: {error}")
# Ошибка: 'str' object does not support item assignment


# ====================================================================
# Пример 12. Ловушка: изменение списка во время итерации
# ====================================================================
tasks = ["done", "done", "draft"]
for task in tasks:
    if task == "done":
        tasks.remove(task)
print("После некорректного удаления:", tasks)
# После некорректного удаления: ['done', 'draft']

# правильный способ: собрать новый список, не трогая исходный во время обхода
tasks = ["done", "done", "draft"]
tasks_left = [task for task in tasks if task != "done"]
print("Через генератор списка (правильно):", tasks_left)
# Через генератор списка (правильно): ['draft']