methods.py

"""
Instance Methods Exercises - Complete the classes below
Run this file with: python topic.py
Or work interactively with: python3 -i topic.py
"""

# Exercise 1: Basic Instance Methods
class Calculator:
    """A simple calculator class demonstrating instance methods."""
    
    def __init__(self, initial_value=0):
        """Initialize calculator with starting value."""
        # Your code here
        pass
    
    def add(self, value):
        """Add value to current result."""
        # Your code here
        pass
    
    def subtract(self, value):
        """Subtract value from current result."""
        # Your code here
        pass
    
    def multiply(self, value):
        """Multiply current result by value."""
        # Your code here
        pass
    
    def divide(self, value):
        """Divide current result by value."""
        # Your code here - handle division by zero
        pass
    
    def get_result(self):
        """Return current result."""
        # Your code here
        pass
    
    def reset(self):
        """Reset calculator to zero."""
        # Your code here
        pass

# Exercise 2: Methods with Self Parameter
class Counter:
    """A counter that can increment, decrement, and track state."""
    
    def __init__(self, start=0, step=1):
        """Initialize counter with starting value and step size."""
        # Your code here
        pass
    
    def increment(self):
        """Increase counter by step size."""
        # Your code here
        pass
    
    def decrement(self):
        """Decrease counter by step size."""
        # Your code here
        pass
    
    def get_value(self):
        """Return current counter value."""
        # Your code here
        pass
    
    def set_value(self, value):
        """Set counter to specific value."""
        # Your code here
        pass
    
    def is_positive(self):
        """Return True if counter is positive."""
        # Your code here
        pass

# Exercise 3: Methods that Modify Object State
class TodoList:
    """A todo list that manages tasks."""
    
    def __init__(self):
        """Initialize empty todo list."""
        # Your code here
        pass
    
    def add_task(self, task):
        """Add a new task to the list."""
        # Your code here
        pass
    
    def complete_task(self, task):
        """Mark a task as completed."""
        # Your code here
        pass
    
    def remove_task(self, task):
        """Remove a task from the list."""
        # Your code here
        pass
    
    def get_pending_tasks(self):
        """Return list of tasks not yet completed."""
        # Your code here
        pass
    
    def get_completed_tasks(self):
        """Return list of completed tasks."""
        # Your code here
        pass
    
    def get_task_count(self):
        """Return total number of tasks."""
        # Your code here
        pass

def run_tests():
    """Test all the classes to verify they work correctly."""
    print("Testing Calculator:")
    calc = Calculator(10)
    calc.add(5)
    print(f"10 + 5 = {calc.get_result()}")  # Should print 15
    calc.multiply(2)
    print(f"15 * 2 = {calc.get_result()}")  # Should print 30
    calc.divide(3)
    print(f"30 / 3 = {calc.get_result()}")  # Should print 10.0
    calc.reset()
    print(f"After reset: {calc.get_result()}")  # Should print 0

    print("\nTesting Counter:")
    counter = Counter(0, 2)  # Start at 0, step by 2
    counter.increment()
    print(f"After increment: {counter.get_value()}")  # Should print 2
    counter.increment()
    print(f"After increment: {counter.get_value()}")  # Should print 4
    counter.decrement()
    print(f"After decrement: {counter.get_value()}")  # Should print 2
    print(f"Is positive: {counter.is_positive()}")     # Should print True

    print("\nTesting TodoList:")
    todo = TodoList()
    todo.add_task("Buy groceries")
    todo.add_task("Walk the dog")
    todo.add_task("Study Python")
    
    print(f"Total tasks: {todo.get_task_count()}")     # Should print 3
    print(f"Pending: {todo.get_pending_tasks()}")      # Should show 3 tasks
    
    todo.complete_task("Buy groceries")
    print(f"After completing one task:")
    print(f"Pending: {len(todo.get_pending_tasks())}")    # Should print 2
    print(f"Completed: {len(todo.get_completed_tasks())}")  # Should print 1

if __name__ == "__main__":
    print("Python Instance Methods Exercises")
    print("=" * 45)
    print("Complete the classes above, then run this file to test them.")
    print("Uncomment the line below when you're ready to test:")
    print()
    # run_tests()  # Uncomment this line to run tests