# sample.py

class Calculator:
    """
    A simple calculator class to perform basic arithmetic operations.
    """

    def __init__(self, value=0):
        """
        Initializes the calculator with a starting value.

        :param value: The starting value of the calculator (default is 0).
        """
        self.value = value

    def add(self, number):
        """
        Adds a number to the current value.

        :param number: The number to add.
        :return: The updated value after addition.
        """
        self.value += number
        return self.value

    def subtract(self, number):
        """
        Subtracts a number from the current value.

        :param number: The number to subtract.
        :return: The updated value after subtraction.
        """
        self.value -= number
        return self.value

    def multiply(self, number):
        """
        Multiplies the current value by a given number.

        :param number: The number to multiply with.
        :return: The updated value after multiplication.
        """
        self.value *= number
        return self.value

    def divide(self, number):
        """
        Divides the current value by the given number.

        :param number: The number to divide by.
        :return: The updated value after division.
        :raises ZeroDivisionError: If the number is zero.
        """
        if number == 0:
            raise ZeroDivisionError("Cannot divide by zero.")
        self.value /= number
        return self.value

    def clear(self):
        """
        Resets the calculator to its initial value (0).

        :return: The reset value (0).
        """
        self.value = 0
        return self.value

def main():
    """
    Main function to demonstrate usage of the Calculator class.

    Creates an instance of the Calculator and performs a series of operations.
    """
    calc = Calculator()
    print(f"Initial value: {calc.value}")
    print(f"Add 10: {calc.add(10)}")
    print(f"Subtract 5: {calc.subtract(5)}")
    print(f"Multiply by 2: {calc.multiply(2)}")
    print(f"Divide by 5: {calc.divide(5)}")
    calc.clear()
    print(f"After clear: {calc.value}")

if __name__ == "__main__":
    main()