  The 21cm line of neutral hydrogen is a powerful probe of the high-redshift
universe (Cosmic Dawn and the Epoch of Reionization), with an unprecedented
potential to inform us about key processes of early galaxy formation, the first
stars and even cosmology and structure formation, via intensity mapping. It is
the subject of a number of current and upcoming low-frequency radio
experiments. This paper presents 21cmSense v2.0, which is a Python package that
provides a modular framework for calculating the sensitivity of these
experiments, in order to enhance the process of their design and forecasting
their power for parameter inference. Version 2.0 of 21cmSense has been
re-written from the ground up to be more modular and extensible than its
venerable predecessor (Pober et al., 2013, 2014), and to provide a more
user-friendly interface. The package is freely available both to use and
contribute towards at https://github.com/rasg-affiliates/21cmSense.
