Venv
Virtual environments create isolated Python environments for different projects. They prevent dependency conflicts by keeping project-specific packages separate from the system-wide Python installation. The guide walks through Creating Virtual Environments, Activating & Deactivating, Installing Packages, requirements.txt, pyproject.toml Basics. `python -m venv .venv` creates a virtual environment in the `.venv` directory. The name `.venv` is conventional and git-ignored by most templates. You can also name it `env`, `venv`, or anything else. Python 3.3+ includes `venv` in the standard library. On Windows: `.venv\Scripts\activate`. On macOS/Linux: `source .venv/bin/activate`. The shell prompt changes to show the active environment. Run `deactivate` to exit. Some editors (VS Code, PyCharm) auto-detect and activate virtual environments. With the environment active, use `pip install package_name` to install packages. `pip install package==1.2.3` installs a specific version. `pip install -r requirements.txt` installs from a requirements file. `pip list` shows installed packages. `pip freeze` lists them in pip format. The guide is organized into 5 sections that build on each other, each pairing a prose explanation with runnable code.