Recap - Simple Calculator

Part of the Object Oriented Programming section of Coddy's Python journey — lesson 8 of 64.

Challenge

Medium

Your Calculator class in calculator.py should:

Have a constructor that initializes a result attribute to 0
Include methods for add, subtract, multiply, and divide that each:
- Take a number as an argument
- Perform the operation between the current result and the number
- Update the result attribute
- Return the new result
Include a clear method that resets the result to 0
Include a get_result method that returns the current result
For the divide method, you must handle division by zero by:
- Checking if the provided number equals 0
- If it is zero, print exactly: "Error: Division by zero"
- Leave the result attribute unchanged in this case
- Return the unchanged result value

The driver.py file will import your Calculator class and test it with code similar to this:

from calculator import Calculator

calc = Calculator()
calc.add(5)       # result becomes 5
calc.multiply(3)  # result becomes 15
calc.subtract(2)  # result becomes 13
calc.divide(0)    # prints "Error: Division by zero", result remains 13
calc.divide(2)    # result becomes 6.5
calc.clear()      # result becomes 0

Follow the TODO comments in the calculator.py file to implement all required functionality.

Cheat sheet

Create a Calculator class with basic arithmetic operations:

class Calculator:
    def __init__(self):
        self.result = 0
    
    def add(self, number):
        self.result += number
        return self.result
    
    def subtract(self, number):
        self.result -= number
        return self.result
    
    def multiply(self, number):
        self.result *= number
        return self.result
    
    def divide(self, number):
        if number == 0:
            print("Error: Division by zero")
            return self.result
        self.result /= number
        return self.result
    
    def clear(self):
        self.result = 0
    
    def get_result(self):
        return self.result

Usage example:

calc = Calculator()
calc.add(5)       # result becomes 5
calc.multiply(3)  # result becomes 15
calc.divide(0)    # prints error, result unchanged

Try it yourself

from calculator import Calculator

# Test case handler
test_case = input()

if test_case == "constructor_test":
    # Test calculator creation and initial state
    calc = Calculator()
    print(f"Initial result: {calc.get_result()}")
    print("Calculator created successfully")

elif test_case == "addition_test":
    # Test addition functionality
    calc = Calculator()
    result1 = calc.add(10)
    print(f"After adding 10: {result1}")
    result2 = calc.add(5)
    print(f"After adding 5: {result2}")
    print(f"Final result: {calc.get_result()}")

elif test_case == "subtraction_test":
    # Test subtraction functionality
    calc = Calculator()
    calc.add(20)  # Start with 20
    result1 = calc.subtract(8)
    print(f"After subtracting 8 from 20: {result1}")
    result2 = calc.subtract(2)
    print(f"After subtracting 2: {result2}")
    print(f"Final result: {calc.get_result()}")

elif test_case == "multiplication_test":
    # Test multiplication functionality
    calc = Calculator()
    calc.add(5)  # Start with 5
    result1 = calc.multiply(4)
    print(f"After multiplying by 4: {result1}")
    result2 = calc.multiply(2)
    print(f"After multiplying by 2: {result2}")
    print(f"Final result: {calc.get_result()}")

elif test_case == "division_test":
    # Test division functionality
    calc = Calculator()
    calc.add(100)  # Start with 100
    result1 = calc.divide(4)
    print(f"After dividing by 4: {result1}")
    result2 = calc.divide(5)
    print(f"After dividing by 5: {result2}")
    print(f"Final result: {calc.get_result()}")

elif test_case == "division_by_zero_test":
    # Test division by zero error handling
    calc = Calculator()
    calc.add(50)
    print(f"Initial value: {calc.get_result()}")
    result = calc.divide(0)  # Should print error message
    print(f"Result after division by zero: {result}")
    print(f"Value unchanged: {calc.get_result()}")

elif test_case == "clear_test":
    # Test clear functionality
    calc = Calculator()
    calc.add(25)
    calc.multiply(3)
    print(f"Before clear: {calc.get_result()}")
    result = calc.clear()
    print(f"After clear: {result}")
    print(f"Current result: {calc.get_result()}")

elif test_case == "comprehensive_test":
    # Test all operations in sequence
    calc = Calculator()
    
    # Perform a series of operations
    calc.add(10)        # result = 10
    calc.multiply(3)    # result = 30
    calc.subtract(5)    # result = 25
    calc.divide(5)      # result = 5
    
    print(f"After sequence of operations: {calc.get_result()}")
    
    # Test error handling
    calc.divide(0)      # Should print error
    print(f"After division by zero attempt: {calc.get_result()}")
    
    # Clear and start fresh
    calc.clear()
    calc.add(100)
    print(f"After clear and add 100: {calc.get_result()}")

else:
    print("Unknown test case")