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Best Practices for Writing Python Functions: A Beginner's Guide

Best Practices for Writing Python Functions

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In this Lesson, we will cover the best practices for writing Python functions, naming conventions, style guidelines, and tips for testing and debugging effectively.

What are Python Functions?

Functions are blocks of code used to perform specific tasks. They are reusable and modular, which means that they can be called from anywhere in your program. Functions take in parameters (inputs) and return a value (output).

For example, let's say we need to perform the same calculation multiple times in our program. Instead of writing the calculation every time we need it, we can write a function that does the calculation for us. We can then call the function whenever we need the result, passing in the necessary parameters.

Naming Conventions and Style Guidelines for Functions

It is important to follow naming conventions and style guidelines when writing Python functions. Here are some best practices to keep in mind:

  • Function names should be descriptive and concise. Use lowercase letters and separate words with underscores (snake_case).

  • Always start your function name with a verb that describes what the function does.

  • Functions should have a docstring, which is a string that explains what the function does, its parameters, and its return value. The docstring should be enclosed in triple quotes.

  • Use four spaces for indentation.

  • Limit your lines to 79 characters or fewer.

  • Use meaningful variable names that describe their purpose.

Here is an example of a properly named and styled function:

def calculate_area_of_circle(radius):
    """Calculate the area of a circle given its radius."""
    pi = 3.14159
    area = pi * radius ** 2
    return area

Modularity and Reusability with Functions

One of the main benefits of functions is that they allow for modularity and reusability in your code. Modularity means breaking down a program into smaller, more manageable pieces. Reusability means that you can reuse these smaller pieces in other parts of your program or in other programs.

Here are some tips for writing modular and reusable functions:

  • Keep your functions small and focused on doing one thing.

  • Avoid using global variables inside your functions. Instead, pass any necessary data as parameters.

  • Use default parameter values to make your functions more flexible.

  • Consider adding error handling to your functions to handle unexpected inputs.

Here is an example of a modular and reusable function:

def calculate_area_of_shape(shape, *args):
    """Calculate the area of a shape given its dimensions."""
    if shape == 'circle':
        radius = args[0]
        return calculate_area_of_circle(radius)
    elif shape == 'rectangle':
        length, width = args
        return length * width
        raise ValueError('Unsupported shape')

Tips for Testing and Debugging Functions Effectively

Testing and debugging are crucial steps in developing reliable and bug-free code. Here are some tips for testing and debugging functions effectively:

  • Write test cases for your functions that cover different scenarios and edge cases.

  • Use print statements to debug your code and see what values are being returned by your functions.

  • Use the Python debugger (pdb) to step through your code and track down errors.

  • Use assertions to check that your functions are returning the expected output.

Here is an example of a test case for our previous function:

def test_calculate_area_of_circle():
    assert round(calculate_area_of_circle(2), 2) == 12.57


By following these best practices for writing Python functions, you can write clean, modular, and reusable code that is easier to test and debug. Remember to keep your function names descriptive, add docstrings, use meaningful variable names, and write test cases to ensure your functions are working correctly. With practice, you can become a proficient programmer capable of writing complex programs with ease.


Robort Gabriel

Lagos, Nigeria

Freelance Web Developer, Native Android Developer, and Coding Tutor.

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