Guidelines for Writing Clean and Maintainable Python Functions

1. Simplicity and Clarity

Keep It Simple: Avoid unnecessary complexity. Each function should do one thing and do it well.

Descriptive Naming: Use clear, descriptive names for functions and variables. Avoid abbreviations unless they are widely understood.

Type Annotations: Use type hints to clarify what types of arguments a function expects and what it returns.

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def calculate_area(radius: float) -> float:
    return 3.14 * radius * radius

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2. Avoid Hardcoding

Use Constants: Define constants for values that shouldn't change. Avoid magic numbers.

Parameterization: Make functions flexible by passing parameters instead of hardcoding values. python

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PI = 3.14159

def calculate_circumference(radius: float, pi: 
                            float = PI) -> float:
    return 2 * pi * radius

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3. Readability

Docstrings: Include a docstring that explains what the function does, its parameters, and its return value.

Consistent Indentation: Stick to 4 spaces per indentation level.

Avoid Long Lines: Break lines at 79 characters where possible.

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def calculate_bmi(weight: float, height: float) -> float:
    """
    Calculate the Body Mass Index (BMI).

    :param weight: Weight in kilograms.
    :param height: Height in meters.
    :return: BMI value.
    """
    return weight / (height ** 2)

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4. Testing and Error Handling

Input Validation: Check for invalid inputs and handle them gracefully.

Unit Tests: Write tests for each function. Ensure edge cases are covered.

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def divide_numbers(numerator: float, denominator: float) -> float:
    if denominator == 0:
        raise ValueError("Denominator cannot be zero.")
    return numerator / denominator

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5. Performance

Efficiency: Avoid unnecessary computations. Optimize for performance if the function will be called frequently or handle large data sets.

Avoid Global State: Don’t rely on or modify global variables

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def is_prime(n: int) -> bool:
    if n <= 1:
        return False
    if n <= 3:
        return True
    if n % 2 == 0 or n % 3 == 0:
        return False
    i = 5
    while i * i <= n:
        if n % i == 0 or n % (i + 2) == 0:
            return False
        i += 6
    return True

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6. DRY Principle

Don’t Repeat Yourself: Reuse code by abstracting common functionality into separate functions or modules.

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def get_positive_input(prompt: str) -> float:
    value = float(input(prompt))
    if value <= 0:
        raise ValueError("Input must be a +ve number.")
    return value

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