  We describe Rabacus, a Python package for calculating the transfer of
hydrogen ionizing radiation in simplified geometries relevant to astronomy and
cosmology. We present example solutions for three specific cases: 1) a
semi-infinite slab gas distribution in a homogeneous isotropic background, 2) a
spherically symmetric gas distribution with a point source at the center, and
3) a spherically symmetric gas distribution in a homogeneous isotropic
background. All problems can accommodate arbitrary spectra and density profiles
as input. The solutions include a treatment of both hydrogen and helium, a
self-consistent calculation of equilibrium temperatures, and the transfer of
recombination radiation. The core routines are written in Fortran 90 and then
wrapped in Python leading to execution speeds thousands of times faster than
equivalent routines written in pure Python. In addition, all variables have
associated units for ease of analysis. The software is part of the Python
Package Index and the source code is available on Bitbucket at
https://bitbucket.org/galtay/rabacus . In addition, installation instructions
and a detailed users guide are available at http://pythonhosted.org//rabacus .
