Pre-installation: download the opacity data

Before you install pRT, please download the opacity data, at least the low-resolution version (\(\lambda/\Delta\lambda=1000\)), as it provides all relevant input files for pRT to run, and contains the necessary folder structure if you want to install high-resolution opacities later (\(\lambda/\Delta\lambda=10^6\)).

Thus, to get started download the opacity and input data (12.1 GB), unzip them, and put the “input_data” folder somewhere on your computer (it does not matter where).

Next, please add the following environment variable to your “.bash_profile” or “.bashrc” file (depending on your operating system) by typing

echo 'export pRT_input_data_path="absolute/path/of/the/folder/input_data"' >>~/.bash_profile

for Mac OS and

echo 'export pRT_input_data_path="absolute/path/of/the/folder/input_data"' >>~/.bashrc

for Linux. Now you are ready to go and can proceed with the actual installation of pRT.


Don’t forget to adapt the path in the line above! If you are uncertain what the absolute path of the input_data folder is, then switch to that folder in the terminal, type “pwd”, and press Enter. You can then just copy-paste that path. Then close and reopen the terminal such that it will read the environment variable correctly.

If you want to also use high-resolution opacity data please follow these steps here, but note that they can be installed at any point after the pRT installation:

The high resolution (\(\lambda/\Delta\lambda=10^6\)) opacity data (about 240 GB if you want to get all species) can be accessed and downloaded via Keeper here. To install them, create a folder called “line_by_line” in the “input_data/opacities/lines” folder. Then put the folder of the absorber species you downloaded in there.

Installation via pip install

To install pRT via pip install just type

pip install petitRADTRANS

in a terminal. Note that you must also have downloaded the low-resolution opacities either before or after to actually run pRT, see above.

Compiling pRT from source

Download petitRADTRANS from Gitlab, or clone it from GitLab via

git clone
  • In the terminal, enter the petitRADTRANS folder

  • Type the following in the terminal python install, and press Enter.

Testing the installation

Open a new terminal window (this will source the pRT_input_data_path). Then open python and type

from petitRADTRANS import Radtrans
atmosphere = Radtrans(line_species = ['CH4'])

This should produce the following output:

 Read line opacities of CH4...