These base classes are used internally to build PDFs and can also be used to implement custom PDFs.

They offer more or less support and freedom. The general starting point should be the BasePDF

zfit.pdf.BasePDF(obs[, params, dtype, ...])
zfit.pdf.ZPDF(obs, *[, name, label, norm, ...])
zfit.pdf.SimplePDF(*args[, obs])
zfit.pdf.SimpleFunctorPDF(*args[, obs])
zfit.pdf.WrapDistribution(*args[, obs])	Baseclass to wrap tensorflow-probability distributions automatically.
zfit.pdf.BaseFunctor(*args[, obs])