Creating Files with Codex

In this final unit, you’ll explore how Codex can help you create entirely new files and populate them with useful content — just by describing what you want. This includes writing new Python files, generating code from scratch, and setting up files like unit tests.

This hands-on unit focuses on expanding your workflow to include file generation and scaffolding, making Codex a powerful tool not just for editing — but also for building.

Once you’ve launched Codex inside your project directory, try a natural prompt like:

Create a new file called test_math_utils.py with unit tests for math_utils.py

Codex will:

• Create the new file
• Read the functions from math_utils.py
• Generate appropriate test cases using a testing framework like unittest or pytest
• Show you a preview before applying the change

You’ll have the chance to review the proposed content and approve it — or edit the suggestion before it’s applied.

Imagine your file math_utils.py contains this function:

def square(x):
    return x * x

Now you run Codex and type:

Write a test file called test_math_utils.py to test the square function.

Codex might suggest creating a new file with this content:

import unittest
from math_utils import square

class TestMathUtils(unittest.TestCase):
    def test_square(self):
        self.assertEqual(square(2), 4)
        self.assertEqual(square(-3), 9)
        self.assertEqual(square(0), 0)

if __name__ == '__main__':
    unittest.main()

You can then review and approve the file creation and content.

This technique is useful for:

• Generating boilerplate code
• Writing tests or config files
• Creating documentation stubs
• Starting new scripts or tools

You’ll save time by letting Codex scaffold the structure, while you focus on the logic.

In this unit, you learned how to use Codex to create new files and populate them with relevant code using natural language. This helps automate setup tasks and streamline the start of new files or components in your projects.