The goal of the Python Essential Reference is to concisely describe the Python programming language and its large library of standard modules, collectively known as the Python programming "environment." It is arranged into four major parts. First a brief tutorial and introduction is presented, then an informal language reference will cover lexical conventions, functions, statements, control flow, datatypes, classes, and execution models. The third part will cover the Python library, and the final section covers the Python C API that is used to write Python extensions. This book is for the professional who has experience with other systems programming language such as C or C++, and is looking for content that is not embellished with basic introductory material on the Python programming environment.