EmPy is a system for embedding Python expressions and statements in template text. It takes an EmPy source file, processes it, and produces output. This is accomplished via expansions, which are special signals to the EmPy system and are set off by a special prefix (by default the at sign, '@'). It can expand arbitrary Python expressions and statements in this way, as well as a variety of special forms. Textual data not explicitly delimited in this way is sent unaffected to the output, allowing Python to be used in effect as a markup language. Also supported are callbacks via hooks, recording and playback via diversions, and dynamic, chainable filters. The system is highly configurable via command line options and embedded commands.