Python で例外処理を実装するためのベスト プラクティス

try:
    # Code that might raise an exception
except ValueError as e:
    print(f"Value error occurred: {e}")

try:
    # Code that might raise an exception
except Exception as e:  # Catch all exceptions if necessary
    print(f"An error occurred: {e}")

try:
    # Code that might raise an exception
except ValueError as e:
    print(f"Value error: {e}")
else:
    print("No exceptions occurred.")
finally:
    print("This will always be executed.")

import logging

logging.basicConfig(level=logging.ERROR)

try:
    # Code that might raise an exception
except Exception as e:
    logging.error(f"An error occurred: {e}")

try:
    # Code that might raise an exception
except ValueError as e:
    logging.error(f"Value error: {e}")
    raise  # Re-raise the exception

with open('file.txt', 'r') as file:
    content = file.read()

try:
    with open('config.json', 'r') as file:
        config = json.load(file)
except FileNotFoundError:
    print("Config file not found, using defaults.")
    config = {"default": "value"}

try:
    # Code that might raise an exception
except Exception as e:
    pass  # Bad practice - you're ignoring the error

def divide(a, b):
    """
    Divides two numbers.

    :param a: Numerator.
    :param b: Denominator.
    :return: The result of the division.
    :raises ZeroDivisionError: If the denominator is zero.
    """
    if b == 0:
        raise ZeroDivisionError("Cannot divide by zero.")
    return a / b

class InvalidInputError(Exception):
    """Exception raised for invalid inputs."""
    pass

def process_input(value):
    if not isinstance(value, int):
        raise InvalidInputError("Input must be an integer.")
    return value * 2

def test_divide():
    assert divide(10, 2) == 5
    with pytest.raises(ZeroDivisionError):
        divide(10, 0)

# Bad practice: using exceptions for control flow
try:
    while True:
        value = next(iterator)
except StopIteration:
    pass  # End of iteration

try:
    result = process_input(input_value)
except InvalidInputError as e:
    raise ValueError("Failed to process input") from e