PyMC

PyMC is a Python library for modeling using Bayesian methods. It implements Markov chain Monte Carlo (MCMC), offering a number of algorithms, including the Metropolis algorithm, and newer algorithms such as No-U-Turn Sampler (NUTS). The name PyMC3 was used for PyMC's version 3, which was a major (total?) rewrite. Subsequent PyMC versions, 4, 5, etc., go by the name PyMC, and (at least initially) maintain PyMC3's modelling API. PyMC3 was built on a general Python library for such mathematical modeling, Theano (which, in turn was built on a Python library for numerical programming, NumPy). Theano's official development ceased and PyMC developers, for PyMCs use, maintained their own separate revised version called Aesara, and eventually a separate revised version of Aesara called PyTensor.