Virtual Environments & Dependencies

Virtual environments isolate project dependencies, preventing conflicts between different projects.

Why Virtual Environments?

Problem: Different projects need different package versions.

Solution: Create isolated environments for each project.

Creating Virtual Environments

To create a virtual environment, use the venv module included with Python.

Terminal Commands

# Create environment named "myenv"
python -m venv myenv

# Activate (Windows)
myenv\Scripts\activate

# Activate (Mac/Linux)
source myenv/bin/activate

Once activated, your terminal prompt will change (e.g., (myenv) C:\...).

Package Management with pip

pip is the package installer for Python. You use it to install libraries from the Python Package Index (PyPI).

Common Commands

# Install a package
pip install requests

# Install specific version
pip install flask==2.0.1

# Upgrade a package
pip install --upgrade pandas

# Uninstall
pip uninstall numpy

requirements.txt

A requirements.txt file lists all dependencies for a project. This ensures other developers install the exact same versions.

Example File

flask==2.3.0
requests>=2.0.0
gunicorn

Workflow

# Save current environment to file
pip freeze > requirements.txt

# Install everything from file
pip install -r requirements.txt

Modern Packaging: pyproject.toml

Best Practices

Quiz

Key Takeaways

✅ Virtual environments isolate project dependencies.
✅ python -m venv creates environments.
✅ pip manages packages.
✅ requirements.txt lists dependencies.
✅ pyproject.toml is the modern standard.

Keep coding! 🚀