Python Virtual Environments & pip Cheat Sheet

Covers creating and activating virtual environments with venv, installing and pinning packages with pip, and managing requirements files.

1 PageBeginnerApr 5, 2026

Creating & Activating a venv

Create isolated Python environments with the built-in venv module.

bash

python3 -m venv .venv          # Create virtual environmentsource .venv/bin/activate      # Activate (macOS/Linux).venv\Scripts\activate         # Activate (Windows cmd).venv\Scripts\Activate.ps1     # Activate (Windows PowerShell)deactivate                     # Exit the virtual environmentwhich python                   # Confirm interpreter path (should point to .venv)

Installing & Managing Packages

Core pip commands for installing, upgrading, and removing packages.

bash

pip install requests             # Install latest versionpip install requests==2.31.0     # Install exact versionpip install "requests>=2.28,<3"  # Install with version rangepip install -U requests          # Upgrade to latestpip uninstall requests           # Remove a packagepip list                         # List installed packagespip show requests                # Show package detailspip list --outdated              # Show packages with newer versions available

requirements.txt Workflow

Freeze and restore dependencies for reproducible environments.

bash

pip freeze > requirements.txt              # Snapshot installed packagespip install -r requirements.txt            # Install from filepip install -r requirements-dev.txt        # Install dev-only extraspip install --upgrade -r requirements.txt  # Upgrade all pinned packages

Useful pip Flags

Handy flags for common pip workflows.

-e .- Install the current directory in editable/development mode (uses setup.py or pyproject.toml)
--no-cache-dir- Skip pip's package cache, useful in Docker builds to reduce image size
--index-url- Install from a custom package index instead of PyPI
--no-deps- Install a package without pulling in its dependencies
-r <file>- Install packages listed in a requirements file
pip check- Verify installed packages have compatible dependency versions
pip cache purge- Clear pip's local wheel/package cache

Pro Tip

Commit a lockfile-style requirements.txt (or use pip-tools/Poetry) so teammates and CI get identical dependency versions — plain 'pip freeze' output mixes direct and transitive dependencies, which pip-compile keeps separate and reproducible.

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