EmPy 3.3

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, @). EmPy 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.

Expressions are embedded in text with the @(...) notation; variations include conditional expressions with @(...?...!...) and the ability to handle thrown exceptions with @(...$...). As a shortcut, simple variables and expressions can be abbreviated as @variable, @object.attribute, @function(arguments), @sequence [index], and combinations.

Full-fledged statements are embedded with @{...}. Control flow in terms of conditional or repeated expansion is available with @[...]. A @ followed by a whitespace character (including a newline) expands to nothing, allowing string concatenations and line continuations.

Comments are indicated with @# and consume the rest of the line, up to and including the trailing newline. @% indicate "significators," which are special forms of variable assignment intended to specify per-file identification information in a format which is easy to parse externally.

Context name and line number changes can be done with @? and @! respectively. @<...> markups are customizeable by the user and can be used for any desired purpose. Escape sequences analogous to those in C can be specified with @..., and finally a @@ sequence expands to a single literal at sign.