¶Politz2013
Joe Gibbs Politz, Alejandro Martinez, Matthew Milano, Sumner Warren, Daniel Patterson, Junsong Li, Anand Chitipothu, and Shriram Krishnamurthi. 2013. “Python: the full monty”. In Proceedings of the 2013 ACM SIGPLAN international conference on Object oriented programming systems languages & applications (OOPSLA '13). Association for Computing Machinery, New York, NY, USA, 217–232.
¶Abstract
We present a small-step operational semantics for the Python programming language. We present both a core language for Python, suitable for tools and proofs, and a translation process for converting Python source to this core. We have tested the composition of translation and evaluation of the core for conformance with the primary Python implementation, thereby giving confidence in the fidelity of the semantics. We briefly report on the engineering of these components. Finally, we examine subtle aspects of the language, identifying scope as a pervasive concern that even impacts features that might be considered orthogonal.
¶Notes
This is the best description of Python semantics that I've found, and includes a good compendium of horror stories to test against.