Introduction

If you just wish to run the SKIRT code, there is no need for Python. The Python Toolkit for SKIRT (PTS) obviously requires a Python install. However, if you already have a Python install that conforms to the PTS system requirements then you can skip this topic as well.

The instructions in this topic describe how to install one of several available Python distributions on Ubuntu using the command line only, for example logged in to the system through an ssh connection. The installation procedure using the command line on other Unix systems is probably very similar.

The Anaconda distribution

The Anaconda distribution is an open source Python distribution that includes an extensive Python package manager. It offers many additional features, including the option to define and switch between multiple Python environments.

As a first step, you will need a regular, interactive Web browser to locate the appropriate Anaconda installer. In case the target system can be reached only through a command line interface, you will need to use a Web browser on another computer, possibly the computer through which you are logged in to the target system. That being said, follow the steps outlined below to install the Anaconda distribution.

In your interactive Web browser, visit the Anaconda distribution page at https://www.anaconda.com/distribution
Using the options on that page, switch to the correct target operating system (Linux in our example).
Locate the link to the installer for Python 3.7 or later and for the appropriate system architecture (64-bit x86 in most cases).
Right-click on the link, select "Copy Link" from the context menu and paste the result in a plain text editor or terminal window, or otherwise figure out the full absolute URL to the installer. At the time of writing the URL is https://repo.anaconda.com/archive/Anaconda3-2022.05-Linux-x86_64.sh
Login to the target system if you have not already done so, create a temporary directory, and download the installer into that directory:
```
mkdir AnacondaInstaller
cd AnacondaInstaller
wget https://repo.anaconda.com/archive/Anaconda3-2022.05-Linux-x86_64.sh
```
replacing the URL by the appropriate current installer URL.
After the download completes, launch the installer:
```
chmod +rx Anaconda3-2022.05-Linux-x86_64.sh
./Anaconda3-2022.05-Linux-x86_64.sh
```
again replacing the file name by the current installer file name.
Follow the instructions displayed by the installer, accepting the default install location, and responding affirmative when asked whether the installer should initialize Anaconda3 by running conda init.

Note
The Anaconda installer adds several lines of commands to your login script; do not remove these lines.
After the installer completes, you can trash it (or you can do this later):
```
rm Anaconda3-2022.05-Linux-x86_64.sh
cd ..
rm -d AnacondaInstaller
```
Logout and re-login to the target computer so that the commands added to your login script by the Anaconda installer get executed.
When you enter "python" at the command line, the welcome message should now list the Python version you just installed and it should include the name Anaconda.
Install any missing Python packages using the procedure described in the following section (see list of packages required by PTS).

Extra Python packages

To install extra Python packages in your Anaconda environment, follow the steps outlined below.

If you haven't already done so, login to the target system.
To display a list of all installed packages and their version numbers, enter:
```
conda list
```
To determine whether a particular package is installed, add the package name. For example, enter:
```
conda list numpy
```
To install an extra package, use the conda install command. For example, enter:
```
conda install reportlab
```
The conda command will display a list of packages to be installed and/or updated, including any dependencies of the requested package. Enter affirmative when asked whether to proceed.
Repeat the previous steps to install additional packages, or specify multiple packages in the conda install command to install all of them in one go.

Install PTS

You are now ready to install PTS as described in Installing PTS (Unix or macOS).