Testing the Program Locally with Python

When making changes to the program, it is safer and easier to test locally instead of editing files directly on the live site. Python includes a built-in web server that allows the project to run locally in a browser.

This creates a simple development workflow: edit a file, save it, refresh the browser, and immediately see the result before uploading anything to the production server.

Why Use a Local Server?

• Test changes safely on your own computer
• Avoid breaking the live site
• Preview HTML, CSS, and JavaScript in a browser
• Develop faster without repeatedly uploading files

We explored using Ruby for this workflow, but that setup turned out to be more complicated than necessary. Python’s built-in server is simpler and works well for this project.

Check if Python is Installed

Open a terminal and run:

python --version

If that does not work, try:

python3 --version

If Python is installed, a version number should appear.

Installing Python (If It Is Not Installed)

If neither command above works, Python may not be installed on your computer. Python is free and can be downloaded from the official Python website.

Step 1 — Download Python

Go to the official Python download page:

https://www.python.org/downloads/

Click the download button for the latest stable version of Python.

Step 2 — Run the Installer

After downloading the installer, run the installation program.

Important for Windows: Make sure to check the box labeled “Add Python to PATH” before clicking Install.

This option allows the python command to work in the terminal from any folder on your computer.

How to Add Python to PATH (Windows)

1. Run the Python installer.
2. On the first installation screen, look at the bottom of the window.
3. Check the box labeled Add Python to PATH.
4. Then click Install Now.

After installation finishes, open a new terminal window and verify the install:

python --version

Step 3 — Verify Installation

After installation completes, open a new terminal window and run:

python --version

If the installation succeeded, you should now see the Python version number.

Start the Local Server

Open a terminal inside the folder where the project files are located.

cd path/to/project-folder

Then run:

python -m http.server 8000

or on some systems:

python3 -m http.server 8000

This starts a local web server on port 8000.

Open the Project in Your Browser

After starting the server, open your browser and go to:

http://localhost:8000

The project should now load locally, just as if it were running on a website.

Typical Workflow

1. Open the project folder in your code editor.
2. Open a terminal in that folder.
3. Run python -m http.server 8000.
4. Open http://localhost:8000 in the browser.
5. Edit files.
6. Save the file.
7. Refresh the browser to see the changes.

Stopping the Server

Return to the terminal and press:

Ctrl + C

Example Terminal Session

cd analyzer-project
python -m http.server 8000
Serving HTTP on 0.0.0.0 port 8000...

The following example shows what a working session might look like:

Common Mistakes

cd your-project-folder
python -m http.server 8000

http://localhost:8000

python -m http.server 8080

http://localhost:8080

Summary

Running a local Python server allows you to test updates safely before uploading them to the live site. It keeps development simple, reduces risk, and avoids the complexity of heavier development tools.

About “Hot Reload”

This setup does not provide true hot reload. When you make changes to files, you will still need to refresh the browser manually to see the updates.

However, using a local Python server is still very useful because it allows the project to run in a proper web environment and lets you test changes quickly without uploading files to the live site each time.

If needed, it is possible to add true hot reload later using additional tools that automatically refresh the browser when files change. For many development tasks, though, the simple workflow described here is more than sufficient.