Installation

POPPY may be installed one of two different ways.

  1. Using PyPI in the usual manner for Python packages:

    % pip install poppy --upgrade
    
  2. Cloning the source code hosted in this repository on GitHub. It is possible to directly install the latest development version using your locally installed git package:

    % git clone https://github.com/spacetelescope/poppy.git
    % cd poppy
    % pip install -e .
    

Requirements

  • Python 3.9, or more recent.

  • The standard Python scientific stack: numpy, scipy, matplotlib

  • POPPY relies upon the astropy community-developed core library for astronomy.

The following are optional. The first, synphot, is recommended for most users. The other optional installs are only worth adding for speed improvements if you are spending substantial time running calculations. See the appendix on performance optimization for details.

  • synphot enables the simulation of PSFs with proper spectral response to realistic source spectra. Without this, PSF fidelity is reduced. See below for installation instructions for synphot.

  • psutil enables slightly better automatic selection of numbers of processes for multiprocess calculations.

  • pyFFTW. The FFTW library can speed up the FFTs used in multi-plane optical simulations such as coronagraphy or slit spectroscopy. Since direct imaging simulations use a discrete matrix FFT instead, direct imaging simulation speed is unchanged. pyFFTW is recommended if you expect to perform many coronagraphic calculations, particularly for MIRI. (Note: POPPY previously made use of the PyFFTW3 package, which is different from pyFFTW. The latter is more actively maintained and supported today, hence the switch. Note also that some users have reported intermittent stability issues with pyFFTW for reasons that are not yet clear.) At this time we recommend most users should skip installing pyFFTW while getting started with poppy.

  • Anaconda accelerate and numexpr. These optionally can provide improved performance particularly in the Fresnel code.

Installing or updating synphot

synphot is an optional dependency, but is highly recommended. See the synphot installation docs here to install synphot and (even more optionally) some of its TRDS data files.

The minimum needed to have stellar spectral models available for use when creating PSFs is synphot itself plus just one of the TRDS data files: the Castelli & Kurucz stellar atlas, file synphot3_castelli-kurucz-2004.tar (18 MB). Feel free to ignore the rest of the many GB of synphot TRDS files unless you know you want a larger set of input spectra or need the reference files for other purposes.

Testing your installation of poppy

Poppy includes a suite of unit tests that exercise its functionality and verify outputs match expectations. If you have cloned the repository, you can optionally run this test suite to verify that your installation is working properly:

% cd poppy/tests/
% pytest
============================ test session starts =====================================
Python 3.7.9, pytest-6.2.3, py-1.9.0, pluggy-0.13.1
... [etc] ...
===================== 166 passed, 9 skipped in 410.12s (0:06:50 ======================

Some tests may be automatically skipped depending on whether certain optional packaged are installed, and other tests in development may be marked “expected to fail” (xfail), but as long as no tests actually fail then your installation is working as expected.