At the command line with pip:

$ pip install lenstronomy

Or, if you have virtualenvwrapper installed:

$ mkvirtualenv lenstronomy
$ pip install lenstronomy

You can also clone the github repository for development purposes.


Make sure the standard python libraries as specified in the requirements. The standard usage does not require all libraries to be installed, in particular the different posterior samplers are only required when being used.

In the following, a few specific cases are mentioned that may require special attention in the installation and settings, in particular when it comes to MPI and HPC applications.


MPI support is provided for several sampling techniques for parallel computing. A specific version of the library schwimmbad is required for the correct support of the moving of the likelihood elements from one processor to another with MPI. Pay attention ot the requirements.


Just-in-time (jit) compilation with numba can provide significant speed-up for certain calculations. There are specific settings for the settings provided as per default, but these may need to be adopted when running on a HPC cluster. You can define your own configuration file in your $XDG_CONFIG_HOME/lenstronomy/config.yaml file. E.g. (check your system for the path):

$ ~/.conf/lenstronomy/config.yaml

following the format of the default configuration which is here.


The fastell4py package, originally from Barkana (fastell), is required to run the PEMD (power-law elliptical mass distribution) lens model and can be cloned from: (needs a fortran compiler). We recommend using the EPL model as it is a pure python version of the same profile.

$ sudo apt-get install gfortran
$ git clone <desired location>
$ cd <desired location>
$ python install --user

Check installation by running tests

You can check your installation with pytest:

$ cd <lenstronomy_repo>
$ py.test

Or you can run a partial test with:

$ cd <lenstronomy_repo>
$ py.test/test/test_LensModel/

You can also run the tests with tox in a virtual environment with:

$ cd <lenstronomy_repo>
$ tox

Note: tox might have trouble with the PyMultiNest installation and the cmake part of it.