PyRes is a complete theorem prover for classical first-order logic. It is not designed for high performance, but to clearly demonstrate the core concepts of a saturating theorem prover.  ...  Equality is handled by adding the basic axioms of equality. PyRes uses the given-clause algorithm, optionally controlled by weight-and age evaluations for clause selection.  ...  Conclusion We have described PyRes, a theorem prover developed as a pedagogical example to demonstrate saturation-based theorem proving in an accessible, readable, welldocumented way.  ...