PBI4 is an FFT-based Python code to measure the power spectrum and bispectrum in real and redshift space of a distribution of particles in a box. It implements up to 4th-order grid interpolation and an interlacing technique to reduce the aliasing contribution arising from the sampling of the density field, as introduced in Sefusatti et al. (2015). PBI4 is an upgrade of the Fortran code PowerI4, which was based on a previous version by Roman Scoccimarro which, in turn, used algorithms developed by Hugh Couchmann. Full info on github.