Using Python's Built-in venv Module

Python’s built-in venv module allows you to create lightweight virtual environments without needing external tools like virtualenv. It’s available in Python 3.3 and newer.

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What is venv?

• Isolated Environment: Each virtual environment is independent and contains its own Python interpreter and libraries.
• Built-in Module: No additional installation is required.

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Creating a Virtual Environment

Use the python command with the -m venv option to create a virtual environment.

Syntax

python -m venv env_name

Examples

1. Create a virtual environment named venv:

python -m venv venv

2. Specify a Python interpreter:

python3.11 -m venv myenv

This ensures the virtual environment uses a specific Python version.

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Activating the Virtual Environment

To start using the virtual environment, you need to activate it.

Windows

venv\Scripts\activate

macOS/Linux

source venv/bin/activate

Once activated, the terminal prompt will display the environment name, e.g., (venv).

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Deactivating the Virtual Environment

To stop using the environment, deactivate it:

deactivate

This returns you to the system’s global Python environment.

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Managing the Environment

Check Installed Packages

To see the installed packages in your virtual environment:

pip list

Install Dependencies

Install packages using pip:

pip install package_name

Save Dependencies

To save all installed packages to a file:

pip freeze > requirements.txt

Reinstall Dependencies

Recreate an environment using the requirements.txt file:

pip install -r requirements.txt

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Deleting the Virtual Environment

To delete a virtual environment, simply remove its directory:

rm -rf venv

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Best Practices with venv

1. Environment Naming:

   • Use descriptive names for your virtual environments, such as my_project_env.

2. Project-Specific Environments:

   • Create the virtual environment within the project folder:

     cd my_project
     python -m venv venv
     

   • Add venv to your .gitignore file to avoid committing it to version control.

3. Keep Dependencies Up-to-Date:

   • Regularly update packages:

     pip install --upgrade pip
     pip list --outdated
     pip install --upgrade package_name
     

4. Use requirements.txt for Reproducibility:

   • Always maintain a requirements.txt file for team collaboration or deployment.