A virtual environment in Python is an isolated workspace that allows you to manage dependencies for a specific project without affecting system-wide or other project dependencies. It ensures that each project has the required libraries and package versions, avoiding conflicts.
1. Why Use Virtual Environments?
Avoid Dependency Conflicts – Different projects can use different versions of the same package.
Keep System Python Clean – Prevent unnecessary installations in the global environment.
Easier Deployment – Ensure projects run with the correct dependencies.
Reproducibility – Share the exact dependencies with others using requirements.txt.
2. Creating a Virtual Environment
Python provides the built-in venv module to create virtual environments.
2.1 Create a Virtual Environment
python -m venv myenv
This creates a folder myenv/ with a local Python environment.
3. Activating a Virtual Environment
You need to activate the virtual environment before installing packages.
3.1 On Windows (Command Prompt)
myenv\Scripts\activate
You should see (myenv) appear before the command prompt.
3.2 On Windows (PowerShell)
myenv\Scripts\Activate.ps1
3.3 On macOS/Linux
source myenv/bin/activate
4. Installing Packages in a Virtual Environment
Once activated, you can install packages using pip.
pip install requests numpy
Packages are installed inside myenv/, not system-wide.
4.1 Check Installed Packages
pip list
4.2 Freeze Dependencies
To save installed packages for sharing or deployment:
pip freeze > requirements.txt
This creates a requirements.txt file listing all installed packages.
4.3 Install Dependencies from requirements.txt
To recreate the environment on another system:
pip install -r requirements.txt
5. Deactivating a Virtual Environment
To exit the virtual environment:
deactivate
This returns you to the system Python environment.
6. Deleting a Virtual Environment
Simply delete the myenv/ folder:
rm -rf myenv # macOS/Linux
rmdir /s myenv # Windows
7. Using virtualenv Instead of venv
virtualenv is an older alternative to venv with more features. Install it with:
pip install virtualenv
Create an environment:
virtualenv myenv
8. Using pyenv for Multiple Python Versions
If you need different Python versions for different projects, use pyenv:
pyenv install 3.9.12
pyenv virtualenv 3.9.12 myenv
pyenv activate myenv
9. Summary
| Command | Description |
|---|---|
python -m venv myenv | Create a virtual environment |
myenv\Scripts\activate | Activate (Windows) |
source myenv/bin/activate | Activate (macOS/Linux) |
pip install package_name | Install a package |
pip freeze > requirements.txt | Save dependencies |
pip install -r requirements.txt | Install dependencies |
deactivate | Exit the environment |
rm -rf myenv | Delete the environment |