"""
Урок 14. Знакомство со строками — весь код примеров одним файлом.

Источник: subjects/python-fundamentals/course/lessons/14-python-strings-intro/examples.html
Файл собран автоматически (tools/build_lesson_examples.py): правьте страницу урока.
Запуск: python lesson-14.py
"""



# ====================================================================
# Пример 1. Создание строк: кавычки, тройные строки, тип str
# ====================================================================
single = 'Hello'
double = "Hello"
multi = """First line
Second line"""
empty = ""

print(single)          # Hello
print(double)           # Hello
print(multi)
# First line
# Second line
print(repr(empty))      # ''
print(type(single))     # <class 'str'>
print(len(single), len(multi))  # 5 22


# ====================================================================
# Пример 2. Неизменяемость строк
# ====================================================================
s = "Hello"
print(id(s))          # 2171595019120 (адрес будет другим при каждом запуске)

s2 = s + " world!"
print(s)               # Hello — исходная строка не изменилась
print(s2)               # Hello world!
print(id(s2))            # 2171597817904 — другой объект
print(s is s2)            # False

try:
    s[0] = "h"
except TypeError as error:
    print("TypeError:", error)
    # 'str' object does not support item assignment


# ====================================================================
# Пример 3. Индексация строк
# ====================================================================
text = "Python"
print(text[0])   # P
print(text[2])   # t
print(text[-1])  # n
print(text[-3])  # h

index = 10
if index < len(text):
    print(text[index])
else:
    print("Index out of range")
# Index out of range

try:
    print(text[10])
except IndexError as error:
    print("IndexError:", error)
    # string index out of range


# ====================================================================
# Пример 4. Срезы строк
# ====================================================================
text = "Python programming"
print(text[0:6])      # Python
print(text[:6])       # Python — с начала строки
print(text[7:])       # programming — до конца строки
print(text[:])        # Python programming — копия всей строки
print(text[-11:])     # programming — отрицательный индекс
print(text[0:12:2])   # Pto rg — с шагом 2
print(text[::-1])     # gnimmargorp nohtyP — разворот строки

print(repr(text[14:7]))    # '' — start после end: пустая строка, не ошибка
print(repr(text[-4:-11]))  # ''


# ====================================================================
# Пример 5. Конкатенация и повторение
# ====================================================================
first = "Py"
second = "thon"
print(first + second)   # Python

print("=" * 10)          # ==========
print("ab" * 3)           # ababab

line = "-" * 20
print(line)               # --------------------


# ====================================================================
# Пример 6. Escape-последовательности и raw-строки
# ====================================================================
text = "Line 1\nLine 2\tTabbed"
print(text)
# Line 1
# Line 2	Tabbed

quote = 'It\'s ok'
print(quote)              # It's ok

path = r"C:\Users\Admin\file.txt"
print(path)                # C:\Users\Admin\file.txt — слэши не экранируются

print("Backslash: \\")      # Backslash: \


# ====================================================================
# Пример 7. len(), ord(), chr() и кодировка UTF-8
# ====================================================================
text = "Python"
print(len(text))    # 6
print(len(""))       # 0

print(ord("A"))       # 65
print(ord("a"))        # 97
print(chr(65))          # A
print(chr(97))           # a

text_ru = "Привет"
encoded = text_ru.encode("utf-8")
print(encoded)   # b'\xd0\x9f\xd1\x80\xd0\xb8\xd0\xb2\xd0\xb5\xd1\x82'

decoded = encoded.decode("utf-8")
print(decoded)    # Привет


# ====================================================================
# Пример 8. Оператор in и перебор строки в цикле
# ====================================================================
text = "Python programming"
print("Python" in text)     # True
print("Hello" in text)       # False
print("Java" not in text)     # True

phrase = "Hello, World!"
vowels = "aeiou"
count = 0
for char in phrase.lower():
    if char in vowels:
        count += 1
print(f"Vowels: {count}")     # Vowels: 3

symbol = "o"
count2 = 0
for char in phrase:
    if char == symbol:
        count2 += 1
print(f"Symbol '{symbol}' appears {count2} time(s).")
# Symbol 'o' appears 2 time(s).
print(phrase.count(symbol))     # 2 — то же самое встроенным методом


# ====================================================================
# Пример 9. f-строки — современный способ подставить значения
# ====================================================================
name = "Alice"
age = 30
print(f"Hello, {name}! Next year you will be {age + 1}.")
# Hello, Alice! Next year you will be 31.

pi = 3.14159265
print(f"Pi rounded: {pi:.2f}")  # Pi rounded: 3.14


# ====================================================================
# Пример 10. Базовые строковые методы
# ====================================================================
raw = "  Hello, Python!  "
print(repr(raw.strip()))                 # 'Hello, Python!'
print(raw.upper())                        # "  HELLO, PYTHON!  "
print(raw.lower())                         # "  hello, python!  "
print(raw.replace("Python", "World"))       # "  Hello, World!  "
print(raw.find("Py"))                        # 9
print(raw.startswith("  He"))                 # True
print(raw.split(", "))                         # ['  Hello', 'Python!  ']

print(raw)  # "  Hello, Python!  " — исходная строка не изменилась


# ====================================================================
# Пример 11. Задача из лекции: палиндром
# ====================================================================
def check_palindrome(value):
    return value == value[::-1]


for sample in ("radar", "hello"):
    result = "The string is a palindrome" if check_palindrome(sample) else "The string is not a palindrome"
    print(f"{sample!r}: {result}")
# 'radar': The string is a palindrome
# 'hello': The string is not a palindrome


# ====================================================================
# Пример 12. Задача из лекции: дешифровка шифра Цезаря
# ====================================================================
def caesar_decrypt(encrypted_text, shift):
    decrypted_text = ""
    i = 0
    while i < len(encrypted_text):
        char = encrypted_text[i]
        decrypted_char = chr(ord(char) - shift)
        decrypted_text += decrypted_char
        i += 1
    return decrypted_text


print(caesar_decrypt("khoor", 3))  # hello