pymc Markov Chain Monte Carlo sampling toolkit. Bayesian estimation, particularly using Markov chain Monte Carlo (MCMC), is an increasingly relevant approach to statistical estimation. However, few statistical software packages implement MCMC samplers, and they are non-trivial to code by hand. ``pymc`` is a python package that implements the Metropolis-Hastings algorithm as a python class, and is extremely flexible and applicable to a large suite of problems. ``pymc`` includes methods for summarizing output, plotting, goodness-of-fit and convergence diagnostics. ``pymc`` only requires ``NumPy``. All other dependencies such as ``matplotlib``, ``SciPy``, ``pytables``, ``sqlite`` or ``mysql`` are optional. Christopher Fonnesbeck, Anand Patil and David Huard 333a2c82b63977de5073e5238491564dd26c0395 2.0