# Galaxy Dependencies Management

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## Learning Questions
- How does Galaxy manage dependencies?
- What is the virtualenv used for?
- Where do JavaScript dependencies come from?

## Learning Objectives
- Understand Python dependency management
- Understand JavaScript dependency management
- Learn about the wheels server

## Dependencies - Python

`script/common_startup.sh` sets up a `virtualenv` with required dependencies in `$GALAXY_ROOT/.venv` (or `$GALAXY_VIRTUAL_ENV` if set).

- Check for existing virtual environment, if it doesn't exist check for `virtualenv`.
- If `virtualenv` exists, use it. Otherwise download it as a script and setup a virtual environment using it.
- `. "$GALAXY_VIRTUAL_ENV/bin/activate"`
- Upgrade to latest `pip` to allow use of binary wheels.
- `pip install -r requirements.txt --index-url [https://wheels.galaxyproject.org/simple`](https://wheels.galaxyproject.org/simple`)
- Install dozens of dependencies.

## Dependencies - JavaScript

- Dependencies are defined in `client/package.json`.
- These are fetched from npm and compiled into bundles as part of `make client` and related `Makefile` targets.

## Key Takeaways
- Python: virtualenv with pip and wheels from galaxyproject.org
- JavaScript: npm/yarn with package.json
- No compilation required by default
- Binary wheels for fast installation