Dependency Manager

Dependency Manager

Manage Python project dependencies with UV, pip-tools, or requirements.txt.

Quick Start

Choose UV for new projects (fast, modern), pip-tools for existing pip workflows, or requirements.txt for simple projects.

Instructions

Choosing a Tool

UV - Fast, modern Python package manager (recommended):

• Extremely fast dependency resolution (10-100x faster than pip)
• Automatic virtual environment management
• Drop-in replacement for pip and pip-tools
• Lock file support with uv.lock
• Best for: All projects, especially new ones

pip-tools - Lightweight, pip-compatible workflow:

• Generates lock files from requirements.in
• Works with existing pip workflows
• Minimal changes to project structure
• Best for: Existing projects, CI/CD with pip, gradual adoption

requirements.txt - Simple, universal:

• Direct pip install
• No additional tools
• No lock file (unless manually maintained)
• Best for: Simple scripts, minimal dependencies, quick prototypes

UV Setup (Recommended)

Install UV:

curl -LsSf https://astral.sh/uv/install.sh | sh
# Or with pip
pip install uv

Initialize new project:

uv init my-project
cd my-project

Add dependencies:

# Runtime dependency
uv add requests

# Development dependency
uv add --dev pytest

# With version constraint
uv add "requests>=2.28.0,<3.0.0"

Install dependencies:

uv sync

Update dependencies:

# Update all
uv lock --upgrade

# Update specific package
uv lock --upgrade-package requests

Remove dependencies:

uv remove requests

Show dependency tree:

uv tree

Export to requirements.txt:

uv pip compile pyproject.toml -o requirements.txt

Run commands in virtual environment:

uv run python script.py
uv run pytest

pip-tools Setup

Install pip-tools:

pip install pip-tools

Create requirements.in:

# requirements.in
requests>=2.28.0
flask>=2.0.0

Create requirements-dev.in:

# requirements-dev.in
-c requirements.txt  # Constrain to production versions
pytest>=7.0.0
black>=23.0.0
mypy>=1.0.0

Compile lock files:

# Compile production dependencies
pip-compile requirements.in

# Compile dev dependencies
pip-compile requirements-dev.in

This generates requirements.txt and requirements-dev.txt with pinned versions.

Install dependencies:

pip-sync requirements.txt requirements-dev.txt

Update dependencies:

# Update all
pip-compile --upgrade requirements.in

# Update specific package
pip-compile --upgrade-package requests requirements.in

Add new dependency:

1. Add to requirements.in
2. Run pip-compile requirements.in
3. Run pip-sync requirements.txt

requirements.txt Workflow

Create requirements.txt:

pip freeze > requirements.txt

Install dependencies:

pip install -r requirements.txt

Separate dev dependencies:

Create requirements-dev.txt:

-r requirements.txt
pytest>=7.0.0
black>=23.0.0

Install with:

pip install -r requirements-dev.txt

Version Constraints

UV/PEP 621 syntax (pyproject.toml):

[project]
dependencies = [
    "requests>=2.28.0,<3.0.0",  # Range
    "flask~=2.0.0",              # Compatible release
    "django>=3.2,<4.0",          # Range
    "numpy==1.24.0",             # Exact version
]

pip syntax (requirements.in or requirements.txt):

requests>=2.28.0,<3.0.0
flask~=2.0.0
django>=3.2,<4.0
numpy==1.24.0
pandas

Constraint operators:

• ==: Exact version
• >=, <=: Minimum/maximum version
• ~=: Compatible release (patch updates)
• ,: Combine constraints (AND)

Dependency Groups

UV/PEP 621 groups:

[project.optional-dependencies]
dev = ["pytest>=7.0.0", "black>=23.0.0"]
docs = ["sphinx>=5.0.0"]
test = ["coverage>=7.0.0"]

Install specific groups:

uv sync --extra dev
uv sync --extra docs
uv sync --all-extras

pip-tools approach:

Create separate .in files:

• requirements.in - Production
• requirements-dev.in - Development
• requirements-test.in - Testing
• requirements-docs.in - Documentation

Resolving Conflicts

With UV:

1. Check conflict:

   uv add package-name
   # UV will show conflict if it exists
   

2. Update constraints in pyproject.toml:

   [project]
   dependencies = [
       "package-a>=2.0.0",  # Relax constraint
       "package-b>=3.0.0",
   ]
   

3. Force resolution:

   uv lock
   uv sync
   

With pip-tools:

1. Check conflict:

   pip-compile requirements.in
   # Will show resolution errors
   

2. Adjust constraints in requirements.in:

   package-a>=2.0.0  # Relax constraint
   package-b>=3.0.0
   

3. Recompile:

   pip-compile requirements.in
   

Common conflict patterns:

• Transitive dependency conflict: Two packages require incompatible versions of a third package

  • Solution: Update one or both packages, or relax constraints

• Python version conflict: Package requires newer Python than project supports

  • Solution: Upgrade Python version or find alternative package

• Platform-specific conflict: Package not available on current platform

  • Solution: Use platform markers or optional dependencies

Platform-Specific Dependencies

UV/PEP 621:

[project]
dependencies = [
    "pywin32>=305; sys_platform == 'win32'",
    "python-daemon>=2.3; sys_platform == 'linux'",
]

pip:

pywin32>=305; sys_platform == 'win32'
python-daemon>=2.3; sys_platform == 'linux'

Optional Dependencies

UV/PEP 621:

[project.optional-dependencies]
aws = ["boto3>=1.26.0"]
all = ["boto3>=1.26.0"]  # Include all optional deps

Install with:

uv sync --extra aws
uv pip install package-name[aws]

Virtual Environments

UV (automatic):

# UV creates and manages venv automatically
uv sync
uv run python script.py
source .venv/bin/activate  # Manual activation if needed

pip-tools (manual):

# Create venv
python -m venv venv

# Activate
source venv/bin/activate  # Linux/Mac
venv\Scripts\activate     # Windows

# Install
pip-sync requirements.txt

requirements.txt (manual):

python -m venv venv
source venv/bin/activate
pip install -r requirements.txt

CI/CD Integration

UV in CI (recommended):

# .github/workflows/test.yml
- name: Install UV
  run: curl -LsSf https://astral.sh/uv/install.sh | sh

- name: Install dependencies
  run: uv sync

- name: Run tests
  run: uv run pytest

pip-tools in CI:

- name: Install dependencies
  run: |
    pip install pip-tools
    pip-sync requirements.txt requirements-dev.txt

- name: Run tests
  run: pytest

requirements.txt in CI:

- name: Install dependencies
  run: pip install -r requirements.txt

- name: Run tests
  run: pytest

Migration Strategies

From requirements.txt to UV:

1. Initialize UV project:

   uv init --no-readme
   

2. Import dependencies:

   # Add each dependency from requirements.txt
   cat requirements.txt | grep -v "^#" | xargs -I {} uv add {}
   

3. Separate dev dependencies:

   uv add --dev pytest black mypy
   

4. Test:

   uv sync
   uv run pytest
   

From requirements.txt to pip-tools:

1. Rename requirements.txt:

   mv requirements.txt requirements.in
   

2. Compile lock file:

   pip-compile requirements.in
   

3. Create dev requirements:

   echo "-c requirements.txt" > requirements-dev.in
   echo "pytest" >> requirements-dev.in
   pip-compile requirements-dev.in
   

4. Test:

   pip-sync requirements.txt requirements-dev.txt
   

From pip-tools to UV:

1. Create pyproject.toml:

   uv init --no-readme
   

2. Import from requirements.in:

   cat requirements.in | grep -v "^#" | grep -v "^-" | xargs -I {} uv add {}
   

3. Test:

   uv sync
   

Common Patterns

Monorepo with Shared Dependencies

UV workspace:

# Root pyproject.toml
[tool.uv.workspace]
members = ["packages/*"]

# packages/package1/pyproject.toml
[project]
name = "package1"
dependencies = ["requests>=2.28.0"]

# packages/package2/pyproject.toml
[project]
name = "package2"
dependencies = ["requests>=2.28.0"]

pip-tools approach:

# shared-requirements.in
requests>=2.28.0

# package1/requirements.in
-c ../shared-requirements.txt
flask>=2.0.0

# package2/requirements.in
-c ../shared-requirements.txt
django>=4.0.0

Lock File Best Practices

Commit lock files:

• uv.lock - Always commit
• requirements.txt (from pip-compile) - Always commit
• requirements.txt (from pip freeze) - Consider committing

Update regularly:

# UV
uv lock --upgrade

# pip-tools
pip-compile --upgrade requirements.in

Verify after updates:

# Run tests
uv run pytest

# Check for security issues
pip-audit

Troubleshooting

UV lock takes too long:

• UV is typically very fast; if slow, check for network issues
• Use uv lock --offline to use cached packages
• Check for circular dependencies

pip-compile fails with conflict:

• Relax version constraints in requirements.in
• Use pip-compile --resolver=backtracking for better resolution
• Check for incompatible transitive dependencies

Dependencies not found:

• Verify package name (check PyPI)
• Check Python version compatibility
• Ensure correct index URL (for private packages)
• With UV: uv pip install --index-url https://custom-index.com package

Virtual environment issues:

• Delete and recreate: rm -rf .venv && uv sync
• Check Python version matches project requirements
• UV automatically manages virtual environments

Outdated dependencies:

• Check with: uv tree --outdated or pip list --outdated
• Update carefully, test after each major update
• Use uv lock --upgrade --dry-run to preview changes

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