Modular Code Development

Estimated time: 60 minutes

Overview

Questions

• What are the benefits of writing modular code in terms of maintenance and scalability?
• How can nested code be targeted and improved through modularization?

Objectives

• Understand the key characteristics that make code modular and why it is advantageous.
• Learn strategies for identifying potential modules within complex code to improve readability and reusability.

What is modularity?

---

Modularity refers to the practice of building software from smaller, self-contained, and independent elements. Each element is designed to handle a specific set of tasks, contributing to the overall functionality of the system.

We will explain modular coding in the slides. You can view the slides here.

Modularity (20 min)

Carefully review the following code snippet:

PYTHON

def convert_temperature(temperature, unit):
    if unit == "F":
        # Convert Fahrenheit to Celsius
        celsius = (temperature - 32) * (5 / 9)
        if celsius < -273.15:
            # Invalid temperature, below absolute zero
            return "Invalid temperature"
        else:
            # Convert Celsius to Kelvin
            kelvin = celsius + 273.15
            if kelvin < 0:
                # Invalid temperature, below absolute zero
                return "Invalid temperature"
            else:
                fahrenheit = (celsius * (9 / 5)) + 32
                if fahrenheit < -459.67:
                    # Invalid temperature, below absolute zero
                    return "Invalid temperature"
                else:
                    return celsius, kelvin
    elif unit == "C":
        # Convert Celsius to Fahrenheit
        fahrenheit = (temperature * (9 / 5)) + 32
        if fahrenheit < -459.67:
            # Invalid temperature, below absolute zero
            return "Invalid temperature"
        else:
            # Convert Celsius to Kelvin
            kelvin = temperature + 273.15
            if kelvin < 0:
                # Invalid temperature, below absolute zero
                return "Invalid temperature"
            else:
                return fahrenheit, kelvin
    elif unit == "K":
        # Convert Kelvin to Celsius
        celsius = temperature - 273.15
        if celsius < -273.15:
            # Invalid temperature, below absolute zero
            return "Invalid temperature"
        else:
            # Convert Celsius to Fahrenheit
            fahrenheit = (celsius * (9 / 5)) + 32
            if fahrenheit < -459.67:
                # Invalid temperature, below absolute zero
                return "Invalid temperature"
            else:
                return celsius, fahrenheit
    else:
        return "Invalid unit"

Refactor the code by extracting functions without altering its functionality.

• What functions did you create?
• What strategies did you use to identify them?

Share your answers in the collaborative document.

Solution 1 - Basic

PYTHON

def celsius_to_fahrenheit(celsius):
    """
    Converts a temperature from Celsius to Fahrenheit.

    Args:
        celsius (float): The temperature in Celsius.

    Returns:
        float: The temperature in Fahrenheit.
    """
    return (celsius * (9 / 5)) + 32


def fahrenheit_to_celsius(fahrenheit):
    """
    Converts a temperature from Fahrenheit to Celsius.

    Args:
        fahrenheit (float): The temperature in Fahrenheit.

    Returns:
        float: The temperature in Celsius.
    """
    return (fahrenheit - 32) * (5 / 9)


def celsius_to_kelvin(celsius):
    """
    Converts a temperature from Celsius to Kelvin.

    Args:
        celsius (float): The temperature in Celsius.

    Returns:
        float: The temperature in Kelvin.
    """
    return celsius + 273.15


def kelvin_to_celsius(kelvin):
    """
    Converts a temperature from Kelvin to Celsius.

    Args:
        kelvin (float): The temperature in Kelvin.

    Returns:
        float: The temperature in Celsius.
    """
    return kelvin - 273.15


def check_temperature_validity(temperature, unit):
    """
    Checks if a temperature is valid for a given unit.

    Args:
        temperature (float): The temperature to check.
        unit (str): The unit of the temperature. Must be "C", "F", or "K".

    Returns:
        bool: True if the temperature is valid, False otherwise.
    """
    abs_zero = {"C": -273.15, "F": -459.67, "K": 0}
    if temperature < abs_zero[unit]:
        return False
    return True


def check_unit_validity(unit):
    """
    Checks if a unit is valid.

    Args:
        unit (str): The unit to check. Must be "C", "F", or "K".

    Returns:
        bool: True if the unit is valid, False otherwise.
    """
    if not unit in ["C", "F", "K"]:
        return False
    return True


def convert_temperature(temperature, unit):
    """
    Converts a temperature from one unit to another.

    Args:
        temperature (float): The temperature to convert.
        unit (str): The unit of the temperature. Must be "C", "F", or "K".

    Returns:
        tuple: A tuple containing the converted temperature in Celsius and Kelvin units.

    Raises:
        ValueError: If the unit is not "C", "F", or "K".
        ValueError: If the temperature is below absolute zero for the given unit.

    Examples:
        >>> convert_temperature(32, "F")
        (0.0, 273.15)
        >>> convert_temperature(0, "C")
        (32.0, 273.15)
        >>> convert_temperature(273.15, "K")
        (0.0, -459.67)
    """
    if not check_unit_validity(unit):
        raise ValueError("Invalid unit")
    if not check_temperature_validity(temperature, unit):
        raise ValueError("Invalid temperature")
    if unit == "F":
        celsius = fahrenheit_to_celsius(temperature)
        kelvin = celsius_to_kelvin(celsius)
        return celsius, kelvin
    if unit == "C":
        fahrenheit = celsius_to_fahrenheit(temperature)
        kelvin = celsius_to_kelvin(temperature)
        return fahrenheit, kelvin
    if unit == "K":
        celsius = kelvin_to_celsius(temperature)
        fahrenheit = celsius_to_fahrenheit(celsius)
        return celsius, fahrenheit

if __name__ == "__main__":
    print(convert_temperature(0, "C"))
    print(convert_temperature(0, "F"))
    print(convert_temperature(0, "K"))
    print(convert_temperature(-500, "K"))
    print(convert_temperature(-500, "C"))
    print(convert_temperature(-500, "F"))
    print(convert_temperature(-500, "B"))

Solution 2 - Advanced

PYTHON

class TemperatureConverter:
    """
    A class for converting temperatures between Celsius, Fahrenheit, and Kelvin.
    """

    def __init__(self):
        """
        Initializes the TemperatureConverter object with a dictionary of absolute zero temperatures for each unit.
        """
        self.abs_zero = {"C": -273.15, "F": -459.67, "K": 0}

    def celsius_to_fahrenheit(self, celsius):
        """
        Converts a temperature from Celsius to Fahrenheit.

        Args:
            celsius (float): The temperature in Celsius.

        Returns:
            float: The temperature in Fahrenheit.
        """
        return (celsius * (9 / 5)) + 32

    def fahrenheit_to_celsius(self, fahrenheit):
        """
        Converts a temperature from Fahrenheit to Celsius.

        Args:
            fahrenheit (float): The temperature in Fahrenheit.

        Returns:
            float: The temperature in Celsius.
        """
        return (fahrenheit - 32) * (5 / 9)

    def celsius_to_kelvin(self, celsius):
        """
        Converts a temperature from Celsius to Kelvin.

        Args:
            celsius (float): The temperature in Celsius.

        Returns:
            float: The temperature in Kelvin.
        """
        return celsius + 273.15

    def kelvin_to_celsius(self, kelvin):
        """
        Converts a temperature from Kelvin to Celsius.

        Args:
            kelvin (float): The temperature in Kelvin.

        Returns:
            float: The temperature in Celsius.
        """
        return kelvin - 273.15

    def check_temperature_validity(self, temperature, unit):
        """
        Checks if a given temperature is valid for a given unit.

        Args:
            temperature (float): The temperature to check.
            unit (str): The unit to check the temperature against.

        Returns:
            bool: True if the temperature is valid for the unit, False otherwise.
        """
        if temperature < self.abs_zero[unit]:
            return False
        return True

    def check_unit_validity(self, unit):
        """
        Checks if a given unit is valid.

        Args:
            unit (str): The unit to check.

        Returns:
            bool: True if the unit is valid, False otherwise.
        """
        if unit not in ["C", "F", "K"]:
            return False
        return True

    def convert_temperature(self, temperature, unit):
        """
        Converts a temperature from one unit to another.

        Args:
            temperature (float): The temperature to convert.
            unit (str): The unit of the temperature.

        Returns:
            tuple: A tuple containing the converted temperature in the other two units.
        """
        if not self.check_unit_validity(unit):
            raise ValueError("Invalid unit")
        if not self.check_temperature_validity(temperature, unit):
            raise ValueError("Invalid temperature")
        if unit == "F":
            celsius = self.fahrenheit_to_celsius(temperature)
            kelvin = self.celsius_to_kelvin(celsius)
            return celsius, kelvin
        if unit == "C":
            fahrenheit = self.celsius_to_fahrenheit(temperature)
            kelvin = self.celsius_to_kelvin(temperature)
            return fahrenheit, kelvin
        if unit == "K":
            celsius = self.kelvin_to_celsius(temperature)
            fahrenheit = self.celsius_to_fahrenheit(celsius)
            return celsius, fahrenheit

if __name__ == "__main__":
    converter = TemperatureConverter()
    print(converter.convert_temperature(0, "C"))
    print(converter.convert_temperature(0, "F"))
    print(converter.convert_temperature(0, "K"))
    print(converter.convert_temperature(-500, "K"))
    print(convert_temperature(-500, "C"))
    print(convert_temperature(-500, "F"))
    print(convert_temperature(0, "X"))

Key Points

• Software is built from smaller, self-contained elements, each handling specific tasks.
• Modular code enhances robustness, readability, and ease of maintenance.
• Modules can be reused across projects, promoting efficiency.
• Good modules perform limited, defined tasks and have descriptive names.
• Focus on readability and use tests to guide modularization.