📝 Change Methods in Python 🚀

In object-oriented programming, change methods (often called mutator methods or setters) are responsible for modifying the internal state of an object. They provide a controlled way to update attributes, ensuring that any rules or constraints are respected.

What Are Change Methods?

• Definition: A change method is a function within a class that modifies an object’s data (attributes).

• Purpose: They offer a structured and controlled way to update an attribute so you don’t accidentally violate constraints or introduce inconsistencies.

Example Use Cases

1. Validation: Ensure new values meet specific criteria (e.g., min/max range).

2. Consistency: When one attribute changes, another might need to update automatically.

3. Logging: Record changes or trigger events when certain attributes are modified.

Why Use Change Methods Instead of Direct Attribute Access?

1. Encapsulation

   • You can hide the internal details of how data is stored.

   • The class controls how external code can interact with those details.

2. Validation & Error Handling

   • Check whether incoming data is valid (e.g., a temperature sensor reading must be above -273.15 °C).

   • Raise errors or set defaults when invalid data is supplied.

3. Maintainability

   • If you need to change the way data is stored or processed, you can modify the method without breaking external code.

Basic Structure of a Change Method

Below is a simple example where we manage a machine’s operational speed. Notice how we handle validation in the set_speed method rather than letting the user directly modify speed:

class Machine:
    def __init__(self, max_speed):
        self.__speed = 0
        self.__max_speed = max_speed

    def set_speed(self, new_speed):
        if 0 <= new_speed <= self.__max_speed:
            self.__speed = new_speed
            print(f"Machine speed set to {new_speed}")
        else:
            print(f"Error: speed must be between 0 and {self.__max_speed}")

    def get_speed(self):
        return self.__speed


# Usage
m = Machine(100)
m.set_speed(50)  # Machine speed set to 50
m.set_speed(150)  # Error: speed must be between 0 and 100

Machine speed set to 50
Error: speed must be between 0 and 100