"""
Урок 15. Summary session 4 — весь код примеров одним файлом.

Источник: subjects/python-fundamentals/course/lessons/15-summary-session-4/examples.html
Файл собран автоматически (tools/build_lesson_examples.py): правьте страницу урока.
Запуск: python lesson-15.py
"""



# ====================================================================
# Пример 1. Вывод символов строки по индексу
# ====================================================================
text = input("Enter a word: ")
index = 0

while index < len(text):
    print(f"Index {index}: {text[index]}")
    index += 1


# ====================================================================
# Пример 2. break и continue рядом
# ====================================================================
word = "sky3blue7"
digits = "0123456789"

# break: stop searching as soon as we find the first digit
position = 0
first_digit_index = -1
while position < len(word):
    if word[position] in digits:
        first_digit_index = position
        break
    position += 1

print(f"First digit index: {first_digit_index}")

# continue: skip digits, keep only letters
position = 0
letters_only = ""
while position < len(word):
    char = word[position]
    position += 1
    if char in digits:
        continue
    letters_only += char

print(f"Letters only: {letters_only}")


# ====================================================================
# Пример 3. Конструкция while / else: два сценария
# ====================================================================
# Scenario 1: loop finishes naturally -> else runs
counter = 1
while counter <= 3:
    print(counter)
    counter += 1
else:
    print("Loop completed without break.")

print("---")

# Scenario 2: loop exits via break -> else is skipped
counter = 1
while counter <= 3:
    print(counter)
    if counter == 2:
        break
    counter += 1
else:
    print("This will not print.")


# ====================================================================
# Пример 4. Переворот строки в цикле
# ====================================================================
word = input("Enter a word: ")
reversed_word = ""
position = len(word) - 1

while position >= 0:
    reversed_word += word[position]
    position -= 1

print(f"Reversed: {reversed_word}")
print(f"Reversed via slice: {word[::-1]}")


# ====================================================================
# Пример 5. Срезы строк s[start:end:step]
# ====================================================================
phrase = "Python programming"

print(phrase[2:5])      # from index 2 up to (not including) index 5
print(phrase[:3])       # from the start up to index 3
print(phrase[::2])      # every second character
print(phrase[::-1])     # full reverse: negative step
print(phrase[-11:-4])   # negative indices count from the end


# ====================================================================
# Пример 6. Сравнение строк лексикографически
# ====================================================================
print("apple" < "banana")   # 'a' < 'b' -> True
print("Apple" < "apple")    # 'A' (65) < 'a' (97) -> True
print(ord("A"), ord("a"))

word1 = "apple"
word2 = "Apple"
print(word1 == word2)               # case-sensitive comparison
print(word1.lower() == word2.lower())  # ignore case


# ====================================================================
# Пример 7. Генератор короткого пароля
# ====================================================================
import random

letters = "abcdefghijklmnopqrstuvwxyz"
password = ""
length = 8
index = 0

while index < length:
    password += random.choice(letters)
    index += 1

print(f"Generated password: {password}")


# ====================================================================
# random.randint(): случайное целое число
# ====================================================================
import random

words = ["python", "loop", "string", "random"]
random_index = random.randint(0, len(words) - 1)
print(f"Random index: {random_index}")
print(f"Chosen word: {words[random_index]}")

attempts_allowed = random.randint(3, 5)
print(f"Attempts allowed: {attempts_allowed}")


# ====================================================================
# Пример 9. Поиск подстроки через цикл
# ====================================================================
text = input("Enter a line: ")
target = "Python"

# Simple way
print(f"Contains '{target}': {target in text}")

# Loop way: case-insensitive search with early exit
lower_text = text.lower()
lower_target = target.lower()
found = False
index = 0

while index <= len(lower_text) - len(lower_target):
    if lower_text[index:index + len(lower_target)] == lower_target:
        found = True
        break
    index += 1

print(f"Found via loop (case-insensitive): {found}")


# ====================================================================
# Пример 10. Коды символов в диапазоне
# ====================================================================
start = int(input("Enter start code: "))
stop = int(input("Enter stop code: "))

while start <= stop:
    print(f"{start}: {chr(start)}")
    start += 1