"""
Урок 39. Summary session 10 — весь код примеров одним файлом.

Источник: subjects/python-fundamentals/course/lessons/39-summary-session-10/examples.html
Файл собран автоматически (tools/build_lesson_examples.py): правьте страницу урока.
Запуск: python lesson-39.py
"""



# ====================================================================
# Пример 1. Базовый набор методов словаря: fromkeys, get, setdefault
# ====================================================================
data = dict.fromkeys(["x", "y", "z"], 0)
print(data)

user = {"name": "Alice", "age": 30}
print(user.get("age"))
print(user.get("city", "Unknown"))

counters = {}
counters.setdefault("visits", 0)
counters["visits"] += 1
counters.setdefault("visits", 0)
counters["visits"] += 1
print(counters)
# {'x': 0, 'y': 0, 'z': 0}
# 30
# Unknown
# {'visits': 2}


# ====================================================================
# Пример 2. Ловушка dict.fromkeys(): общая ссылка на изменяемый объект
# ====================================================================
keys = ["x", "y"]
shared_list = []
shared = dict.fromkeys(keys, shared_list)
shared["x"].append(1)
print(shared)

independent = {key: [] for key in keys}
independent["x"].append(1)
print(independent)
# {'x': [1], 'y': [1]}
# {'x': [1], 'y': []}


# ====================================================================
# Пример 3. keys(), values(), items() — динамические view, а не снимок
# ====================================================================
data = {"name": "Alice", "age": 30}
live_keys = data.keys()
print(live_keys)
data["city"] = "New York"
print(live_keys)

snapshot = list(data.keys())
data["country"] = "USA"
print(snapshot)
print(list(data.keys()))
# dict_keys(['name', 'age'])
# dict_keys(['name', 'age', 'city'])
# ['name', 'age', 'city']
# ['name', 'age', 'city', 'country']


# ====================================================================
# Пример 4. Вложенные словари: доступ по цепочке ключей и обход
# ====================================================================
school = {
    "class1": {"students": ["Alice", "Bob"], "teacher": "Mrs. Smith"},
    "class2": {"students": ["Carol"], "teacher": "Mr. Lee"},
}
print(school["class1"]["students"][0])

for class_name, info in school.items():
    print(class_name, "-", info["teacher"], "-", len(info["students"]), "students")
# Alice
# class1 - Mrs. Smith - 2 students
# class2 - Mr. Lee - 1 students


# ====================================================================
# Пример 5. copy() против copy.deepcopy()
# ====================================================================
import copy

original = {"name": "Alice", "scores": [90, 85]}
shallow = original.copy()
deep = copy.deepcopy(original)

original["name"] = "Bob"
original["scores"].append(80)

print(shallow)
print(deep)
# {'name': 'Alice', 'scores': [90, 85, 80]}
# {'name': 'Alice', 'scores': [90, 85]}


# ====================================================================
# Пример 6. Dict comprehension: преобразование и фильтрация
# ====================================================================
words = ["cat", "elephant", "dog", "hippopotamus"]
lengths = {word: len(word) for word in words}
print(lengths)

long_words = {word: length for word, length in lengths.items() if length > 3}
print(long_words)
# {'cat': 3, 'elephant': 8, 'dog': 3, 'hippopotamus': 12}
# {'elephant': 8, 'hippopotamus': 12}


# ====================================================================
# Пример 7. def, pass, позиционные и именованные аргументы, значения по умолчанию
# ====================================================================
def stub():
    pass


def greet(name, greeting="Hello"):
    return f"{greeting}, {name}!"


print(greet("Alice"))
print(greet("Bob", "Hi"))
print(greet(name="Carol", greeting="Hey"))
# Hello, Alice!
# Hi, Bob!
# Hey, Carol!


# ====================================================================
# Пример 8. *args и **kwargs: упаковка лишних аргументов
# ====================================================================
def describe(*args, **kwargs):
    print("args:", args)
    print("kwargs:", kwargs)


describe(1, 2, 3, name="Alice", age=30)


def total(*numbers):
    return sum(numbers)


print(total(1, 2, 3, 4))
# args: (1, 2, 3)
# kwargs: {'name': 'Alice', 'age': 30}
# 10


# ====================================================================
# Пример 9. return и None, правило LEGB
# ====================================================================
def no_return():
    print("done")


result = no_return()
print(result)

x = 10


def show_value():
    x = 5
    return x


print(show_value())
print(x)
# done
# None
# 5
# 10


# ====================================================================
# Пример 10. global против параметров и return
# ====================================================================
counter = 0


def increment_global():
    global counter
    counter += 1


increment_global()
increment_global()
print(counter)


def increment(value):
    return value + 1


counter2 = 0
counter2 = increment(counter2)
counter2 = increment(counter2)
print(counter2)
# 2
# 2


# ====================================================================
# Пример 11. Практика: валидация скобок стеком и словарём соответствий
# ====================================================================
def is_valid_brackets(text):
    pairs = {")": "(", "]": "[", "}": "{"}
    stack = []
    for char in text:
        if char in pairs.values():
            stack.append(char)
        elif char in pairs:
            if not stack or stack.pop() != pairs[char]:
                return False
    return not stack


print(is_valid_brackets("([)]"))
print(is_valid_brackets("({[]})"))
# False
# True


# ====================================================================
# Пример 12. Практика: словарь + функция вместе — реверс словаря и группировка
# ====================================================================
def reverse_dictionary(data):
    result = {}
    for key, value in data.items():
        result.setdefault(value, []).append(key)
    return result


print(reverse_dictionary({"a": 1, "b": 2, "c": 1, "d": 3}))


def group_students(students):
    groups = {"Отличники": {}, "Хорошисты": {}, "Троечники": {}, "Не сдали": {}}
    for name, score in students.items():
        if score >= 85:
            groups["Отличники"][name] = score
        elif score >= 70:
            groups["Хорошисты"][name] = score
        elif score >= 50:
            groups["Троечники"][name] = score
        else:
            groups["Не сдали"][name] = score
    return groups


students = {"Аня": 92, "Боря": 76, "Ваня": 65, "Галя": 48}
print(group_students(students))
# {1: ['a', 'c'], 2: ['b'], 3: ['d']}
# {'Отличники': {'Аня': 92}, 'Хорошисты': {'Боря': 76}, 'Троечники': {'Ваня': 65}, 'Не сдали': {'Галя': 48}}