Getting started with COMETS
Installation of COMETS prerequisites
There are two software prerequisites for COMETS.
First, users must download and install Java. The minimum version of required 64-bit Java is 1.8.
Second, users should download and install Gurobi. The installation of Gurobi requires a license, which is free for academics. Follow the Gurobi instructions to activate your license before attempting to use COMETS.
If COMETS is struggling to connect to Gurobi, users can begin the troubleshooting process by making sure the GUROBI_HOME environment variable is set. How exactly this is done will depend on the operating system of the user's computer. More information can be found on the COMETS website.
COMETS is now also compatible with GLOP (the Google Linear Optimization Package), which can be installed using pip install ortools. 
Installation of the COMETS software
COMETS can be installed in two ways: using the COMETS installer or by unpacking the .tar.gz file. The installer is available here. Installation for Windows, MacOS, and Linux systems are all available. The installer will guide users through a standard GUI installation procedure.
Alternatively, users can use the comets_x.x.x.tar.gz file for custom installation. More information on this process is available here.
Installation of the COMETS Python Toolbox
While both MATLAB and Python toolboxes exist for COMETS, this tutorial uses Python to implement secondary metabolites.
It is recommended that users install Python (version >=3.6) using the Anaconda distribution or other method as preferred. Anaconda and related methods have the benefit of installing Jupyter Notebooks at the same time. 
The COMETS Python toolbox (cometspy) is available from the package manager PyPI using the pip command.
pip install cometspy
Version issues
There are two important version issues to note when attempting to get started with COMETS and the COMETS Python Toolbox.
- Gurobi versions >10 are no longer compatible with Java
- pandasversions >2 and <1.5 are not compatible with the COMETS- Pythontoolbox
Dependencies
All simulations in this tutorial will rely on 4 Python packages:
- cobra, from which- Model,- Reaction, and- Metaboliteshould be imported
- random
- pandas
- cometspy