Advanced Functional Programming with Callable Objects in Python

Hello! In our journey through functional programming, we've explored currying, partial application, and callable objects. Today, we'll dive into an advanced example using callable objects in combination with Python's powerful higher-order functions and list comprehensions. The goal is to deepen your understanding of how to create and utilize callable objects to make your code more modular and reusable, especially in a real-world context like adjusting employee salaries.

By the end of this lesson, you'll be able to create complex callable objects, apply them to collections using higher-order functions, and understand the benefits of such an approach.

We start by defining a class for employees:

class Employee:
    def __init__(self, name, salary):
        self.name = name
        self.salary = salary

This class holds basic details about an employee, which include their name and salary.

Let's create a callable class that increases salary by a certain factor:

class SalaryIncrease:
    def __init__(self, factor):
        self.factor = factor

    def __call__(self, employee):
        return Employee(employee.name, employee.salary * self.factor)

In this example:

• The constructor __init__(self, factor) initializes the factor used to increase the salary.
• The __call__ method takes an Employee object and returns a new Employee object with the updated salary.

Let's integrate the Employee class and the SalaryIncrease callable into a simple program. We need a collection of employees. We'll use a Python list:

employees = [
    Employee("Alice", 30000),
    Employee("Bob", 45000),
    Employee("Charlie", 32000),
    Employee("David", 52000),
    Employee("Eve", 48000)
]

To apply the 10% salary increase, we instantiate the SalaryIncrease callable:

increase_factor = 1.1  # 10% raise
increase = SalaryIncrease(increase_factor)

We can apply our callable to each employee in the list using the map function:

increased_salaries = list(map(increase, employees))

The map function applies increase to each object in the employees list.