"""
Урок 38. Функции. Области видимости — весь код примеров одним файлом.

Источник: subjects/python-fundamentals/course/lessons/38-functions-scope/examples.html
Файл собран автоматически (tools/build_lesson_examples.py): правьте страницу урока.
Запуск: python lesson-38.py
"""



# ====================================================================
# Пример 1. def, return и None
# ====================================================================
# 01_def_return.py
def greet(name):
    return f"Hello, {name}!"

def validate_data():
    pass   # заготовка: интерфейс понятен, реализации пока нет

print(greet("Alice"))       # Hello, Alice!
print(validate_data())       # None


# ====================================================================
# Пример 2. Позиционные, именованные и default-аргументы
# ====================================================================
# 02_positional_named.py
def describe(name, age, greeting="Hello"):
    return f"{greeting}, {name}! Age: {age}"

print(describe("Bob", 30))
# Hello, Bob! Age: 30

print(describe(age=25, name="Alice", greeting="Hi"))
# Hi, Alice! Age: 25

print(describe("Carol", greeting="Hey", age=40))
# Hey, Carol! Age: 40


# ====================================================================
# Пример 3. Порядок параметров: default — только после обязательных
# ====================================================================
# 03_default_order.py
try:
    exec("def bad(greeting='Hello', name): pass")
except SyntaxError as error:
    print("SyntaxError:", error)
# SyntaxError: non-default argument follows default argument (<string>, line 1)


# ====================================================================
# Пример 4. *args — упаковка позиционных аргументов
# ====================================================================
# 04_args.py
def show_numbers(*args):
    print(args, type(args))

show_numbers(1, 2, 3)
# (1, 2, 3) <class 'tuple'>
show_numbers()
# () <class 'tuple'>

def sum_all(*args):
    return sum(args)

print(sum_all(1, 2, 3, 4))
# 10


# ====================================================================
# Пример 5. **kwargs — упаковка именованных аргументов
# ====================================================================
# 05_kwargs.py
def show_info(**kwargs):
    print(kwargs, type(kwargs))

show_info(name="Alice", age=25, city="Paris")
# {'name': 'Alice', 'age': 25, 'city': 'Paris'} <class 'dict'>


# ====================================================================
# Пример 6. Полный порядок параметров в одной функции
# ====================================================================
# 06_combined_order.py
def show_full_info(name, *details, age=25, **extra):
    return name, details, age, extra

print(show_full_info("Alice", "Developer", age=30, city="New York"))
# ('Alice', ('Developer',), 30, {'city': 'New York'})

print(show_full_info("Bob"))
# ('Bob', (), 25, {})


# ====================================================================
# Пример 7. Распаковка при вызове функции
# ====================================================================
# 07_unpacking_call.py
def add(a, b, c):
    return a + b + c

nums = (1, 2, 3)
print(add(*nums))
# 6

def show_person(name, age, city):
    print(name, age, city)

person = {"name": "Bob", "age": 30, "city": "London"}
show_person(**person)
# Bob 30 London


# ====================================================================
# Пример 8. Только позиционные (/) и только именованные (*)
# ====================================================================
# 08_positional_keyword_only.py
def example(a, b, /, c, *, d):
    return a, b, c, d

print(example(1, 2, 3, d=4))
# (1, 2, 3, 4)

try:
    example(a=1, b=2, c=3, d=4)   # a, b — только позиционные
except TypeError as error:
    print("TypeError:", error)
# TypeError: example() got some positional-only arguments passed as keyword arguments: 'a, b'

try:
    example(1, 2, 3, 4)            # d — только именованный
except TypeError as error:
    print("TypeError:", error)
# TypeError: example() takes 3 positional arguments but 4 were given


# ====================================================================
# Пример 9. LEGB: порядок поиска имени
# ====================================================================
# 09_legb.py
z = "global z"

def outer():
    x = "enclosing x"
    def inner():
        y = "local y"
        print(y, x, z, len)   # local, enclosing, global, built-in
    inner()

outer()
# local y enclosing x global z <built-in function len>


# ====================================================================
# Пример 10. global — изменение глобальной переменной
# ====================================================================
# 10_global.py
counter = 0

def increment_counter():
    global counter
    counter += 1

print("до:", counter)      # до: 0
increment_counter()
increment_counter()
print("после:", counter)   # после: 2

def try_increment_without_global():
    counter = counter + 1   # counter уже считается локальной из-за присваивания ниже

try:
    try_increment_without_global()
except UnboundLocalError as error:
    print("UnboundLocalError:", error)
# UnboundLocalError: cannot access local variable 'counter' where it is not associated with a value


# ====================================================================
# Пример 11. nonlocal — изменение переменной внешней функции
# ====================================================================
# 11_nonlocal.py
def make_accumulator():
    total = 0
    def add_value(value):
        nonlocal total
        total += value
        return total
    return add_value

accumulate = make_accumulator()
print(accumulate(10))   # 10
print(accumulate(5))    # 15
print(accumulate(1))    # 16


# ====================================================================
# Пример 12. Ловушка: изменяемое значение по умолчанию
# ====================================================================
# 12_mutable_default.py
def append_bad(value, items=[]):
    items.append(value)
    return items

print(append_bad(1))   # [1]
print(append_bad(2))   # [1, 2]  — список "запомнил" предыдущий вызов!

def append_good(value, items=None):
    if items is None:
        items = []
    items.append(value)
    return items

print(append_good(1))  # [1]
print(append_good(2))  # [2]