Complete Tutorial: Creating and Testing a Python Project Using a Virtual Environment

This tutorial guides you step-by-step through creating a Python project with a virtual environment and testing it with a simple Python script. Commands are provided for both Linux/macOS and Windows. It also accounts for different Python command usages: python, python3, and py. Examples of all 3 options will be provided. Be sure to use the option that is applicable to your system configuration.

NOTE: This tutorial assumes that you have a basic understanding of your operating system (Windows, macOS, or Linux), familiarity with Python programming fundamentals, and experience using the command line/terminal. If you are new to any of these topics, you may want to review introductory materials before proceeding.

1. Install Python

Make sure Python is installed on your system.

• Check by running one of these commands:

• Linux/macOS options, bash:

  python --version
  python3 --version
  

• Windows (Command Prompt or PowerShell):

  python --version
  python3 --version
  py --version

• If Python is not installed, download it from python.org and install it.

2. Create a Project Directory

Create and navigate to your project folder.

• Linux/macOS:

  mkdir my_python_project
  cd my_python_project

• Windows (CMD / PowerShell):

  mkdir my_python_project
  cd my_python_project

3. Create a Virtual Environment

Create a virtual environment inside your project folder. Use one of the available Python commands depending on your system:

• Linux/macOS options, bash:

  python -m venv .venv
  python3 -m venv .venv

• Windows (CMD / PowerShell) options:

  python -m venv .venv
  python3 -m venv .venv
  py -m venv .venv

This creates a folder named .venv with your virtual environment.

4. Activate the Virtual Environment

Activate the virtual environment to isolate your project dependencies.

• Linux/macOS options, bash:

  source .venv/bin/activate

• Windows Command Prompt (CMD):

  .venv\Scripts\activate.bat

• Windows PowerShell:

  .venv\Scripts\Activate.ps1

After activation, your prompt typically shows (venv).

5. Install Required Packages

For testing, we will install the requests package inside the virtual environment.

Run:

pip install requests

6. Create a Simple Python Test Script

Create a new file named app.py in your project directory and add the following code:

# app.py

import requests

def main():
    print("Virtual environment test: Starting script...")

    try:
        url = "https://www.google.com"
        response = requests.get(url)
        print(f"Fetched {url} with status code: {response.status_code}")
    except Exception as e:
        print(f"Error fetching website: {e}")

    print("Virtual environment test: Script completed successfully.")

if __name__ == "__main__":
    main()

7. Run the Python Script

Run your script using the command that corresponds to your Python setup, with the virtual environment still activated:

• Linux/macOS options, bash:

  python app.py
  python3 app.py

• Windows (CMD / PowerShell) options:

  python app.py
  python3 app.py
  py app.py

You should see output similar to:

Virtual environment test: Starting script...
Fetched https://www.google.com with status code: 200
Virtual environment test: Script completed successfully.

This confirms your virtual environment and Python setup are working correctly.

8. Optional: Save Your Dependencies

Save installed packages to a requirements.txt file:

pip freeze > requirements.txt

This file can be used later to recreate the environment.

9. Deactivate the Virtual Environment

When finished, deactivate your environment by running:

deactivate

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