  Current neutrino detectors will observe hundreds to thousands of neutrinos
from a Galactic supernovae, and future detectors will increase this yield by an
order of magnitude or more. With such a data set comes the potential for a huge
increase in our understanding of the explosions of massive stars, nuclear
physics under extreme conditions, and the properties of the neutrino. However,
there is currently a large gap between supernova simulations and the
corresponding signals in neutrino detectors, which will make any comparison
between theory and observation very difficult. SNEWPY is an open-source
software package which bridges this gap. The SNEWPY code can interface with
supernova simulation data to generate from the model either a time series of
neutrino spectral fluences at Earth, or the total time-integrated spectral
fluence. Data from several hundred simulations of core-collapse, thermonuclear,
and pair-instability supernovae is included in the package. This output may
then be used by an event generator such as sntools or an event rate calculator
such as SNOwGLoBES. Additional routines in the SNEWPY package automate the
processing of the generated data through the SNOwGLoBES software and collate
its output into the observable channels of each detector. In this paper we
describe the contents of the package, the physics behind SNEWPY, the
organization of the code, and provide examples of how to make use of its
capabilities.
