Python 文法

# Online Python Playground
# Use the online IDE to write, edit & run your Python code
# Create, edit & delete files online

class Resource:
    def __enter__(self):
        self.resource = "hoge"
        print(self.resource)
        return self.resource

    def __exit__(self, exc_type, exc_value, traceback):
        print("Resource is now closed")

# Resourceクラスを使用してwithステートメントのスコープをテスト
with Resource() as res:
    print("res in with: ", res)
    test = "test"
    print("test in with: ", test)

print("res in main: ", res)  # withブロック外でaが存在するかを確認
print("test in main: ", test)

def hoge():
    a = 'a'
    print("a in hoge method: ", a)

hoge()
print(a)

def gen_function(n):
    print('start')
    while n:
        print(f'yield: {n}')
        yield n
        print("after n")
        n -= 1

# for i in gen_function(2):
#     print(i)


gen = gen_function(3)
next(gen)
next(gen)
next(gen)
# Output
# ```
# start
# yield: 3
# after n
# yield: 2
# after n
# yield: 1
# ```

# next(gen) # File "<exec>", line 24, in <module>

print([i**2 for i in gen_function(5)]) # [25, 16, 9, 4, 1]

print(gen(5))

def reader(src):
    with open(src) as f:
        for line in f:
            yield line

def convert(line):
    return line.upper()


def writer(dest, reader):
    with open(dest, reader):
        for line in reader:
            f.write(convert(line))

writer('dest.txt', reader('src.txt'))

# 一行ずつメモリに展開されるので、大量のテキストデータでもメモリを圧迫せずに処理を行える

from dataclasses import dataclass

@dataclass
class Fruit:
    name: str
    price: int = 0

apple = Fruit(name="apple", price=128)
print(apple)
print(apple.name)
apple.price = 150
print(apple.price)



class Fruit:
    def __init__(self, name, price):
        self.name = name
        self.price = price


banana = Fruit(name="banana", price=130)
print(banana)
print(banana.name)
banana.price = 160
print(banana.price)

def deco1(f):
    print("deco1 called")
    def wrapper():
        print('before exec')
        v = f()
        print('after exec')
        return v
    return wrapper

@deco1
def func():
    print('exec')
    return 1


func()


def deco2(f):
    def wrapper(*args, **kwargs):
        print('before exec')
        print("args: ", args)
        print("kwargs: ", kwargs)
        v = f(*args, **kwargs)
        print('after exec')
        return v
    return wrapper

@deco2
def func2(x, y):
    print('exec')
    return x, y

func2(1, 2)
# args:  (1, 2)
# kwargs:  {}

@deco2
def func3(a: "a", b: "b"):
    return a, b

func3(a="aa", b="bb")
# args:  ()
# kwargs:  {'a': 'aa', 'b': 'bb'}

# func3() # TypeError: func3() missing 2 required positional arguments: 'a' and 'b'

def deco3(z):
    def _deco3(f):
        def wrapper(*args, **kwargs):
            print('before exec')
            print("z: ", z)
            print("args: ", args)
            print("kwargs: ", kwargs)
            v = f(*args, **kwargs)
            print('after exec')
            return v
        return wrapper
    return _deco3

@deco3(z='z')
def func4(x, y):
    print('x, y: ', x, y)
    return x, y

func4('あ', 'い')

from functools import wraps

def deco(f):
    @wraps(f)
    def wrapper(*args, **kwargs):
        print('before exec')
        v = f(*args, **kwargs)
        print('after exec')
        return v
    return wrapper

@deco
def func():
    """func です"""
    print("exec")


# @wraps(f)がない場合
print(func.__name__) # wrapper
print(func.__doc__) # None


# @wraps(f)がある場合
print(func.__name__) # func
print(func.__doc__) # func です

class TextField:
    def __set_name__(self, owner, name):
        print(f'__set_name__was called')
        print(f'{owner=}, {name=}')
        self.name = name
    
    def __set__(self, instance, value):
        print('__set__ was called')
        if not isinstance(value, str):
            raise AttibuteError('must be str')
        instance.__dict__[self.name] = value
    
    def __get__(self, instance, owner):
        print('__get__ was called')
        return instance.__dict__[self.name]


class Book:
    title = TextField()

book = Book()
book.title = 'Harry Potter'

# 非データデスクリプタ
class TextField2:
    def __init__(self, value):
        if not isinstance(value, str):
            raise AttributeError('must be str')
        self.value = value

    def __set_name__(self, owner, name):
        print(f'__set_name__was called')
        print(f'{owner=}, {name=}')
        self.name = name
    
    def __get__(self, instance, owner):
        print('__get__ was called')
        return self.value
        
class Book2:
    title = TextField2('Python Book')

book = Book2()
book.title # __get__ was called
# インスタンス変数のセット
book.title = 'updated book'
print(book.title) # updated book __get__ は呼ばれない 上書きされる

from collections import defaultdict

# デフォルト値がNoneのdefaultdictを作成
my_dict = defaultdict(lambda: None)

print(my_dict['non_existent_key'])
# None

my_dict2 = {}
print(my_dict2['non_existent_key'])
#   File "<exec>", line 9, in <module>
# KeyError: 'non_existent_key'

from typing import TypedDict

class User(TypedDict):
    name: str
    age: int

user = User(name="sakai", age=30)
print(user["name"]) # sakai

user: User = {
    "name": "Alice",
    "age": 30,
    "email": "alice@example.com"
}

class MyClass:
    def __init__(self):
        self.value = 42

obj = MyClass()

# 'value'という属性がobjに存在するかどうかをチェック
print(hasattr(obj, 'value'))  # 出力: True

# 'nonexistent'という属性がobjに存在するかどうかをチェック
print(hasattr(obj, 'nonexistent'))  # 出力: False

pythonCopyclass Greeter:
    def __init__(self, greeting):
        self.greeting = greeting
    
    def __call__(self, name):
        return f"{self.greeting}, {name}!"

# インスタンスを作成
hello_greeter = Greeter("Hello")

# インスタンスを関数のように呼び出す
result = hello_greeter("Alice")
print(result)  # 出力: Hello, Alice!