Python pip — The Complete Package Manager Guide

pip Basics

# Install a package
pip install flask

# Install specific version
pip install flask==3.0.0

# Install with version constraints
pip install "flask>=2.0,<3.0"

# Upgrade a package
pip install --upgrade flask

# Uninstall a package
pip uninstall flask

# List installed packages
pip list

# Show package info
pip show flask

Requirements Files

# Generate requirements.txt
pip freeze > requirements.txt

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

# Example requirements.txt:
# flask==3.0.0
# requests>=2.31.0
# python-dotenv~=1.0.0

Troubleshooting

# Permission errors
pip install --user flask

# SSL errors
pip install --trusted-host pypi.org flask

# Check which Python pip is using
pip --version

Modern Alternatives

• pip-tools: Pin exact versions
• Poetry: Dependency management + virtual environments
• uv: Extremely fast pip replacement in Rust
• pipx: Install CLI tools in isolated environments