Python Cookbook

Module: Yet Another Python Templating Utility (YAPTU)

Credit: Alex Martelli

Templating is the process of defining a block of text that contains embedded variables, code, and other markup. This text block is then automatically processed to yield another text block, in which the variables and code have been evaluated and the results have been substituted into the text. Most dynamic web sites are generated with the help of templating mechanisms.

Example 3-1 contains Yet Another Python Templating Utility (YAPTU), a small but complete Python module for this purpose. YAPTU uses the sub method of regular expressions to evaluate embedded Python expressions but handles nested statements via recursion and line-oriented statement markers. YAPTU is suitable for processing almost any kind of structured-text input, since it lets client code specify which regular expressions denote embedded Python expressions and/or statements. Such regular expressions can then be selected to avoid conflict with whatever syntax is needed by the specific kind of structured text that is being processed (HTML, a programming language, RTF, TeX, etc.) See Recipe 3.22 for another approach, in a very different Python style, with very similar design goals.

YAPTU uses a compiled re object, if specified, to identify expressions, calling sub on each line of the input. For each match that results, YAPTU evaluates match.group(1) as a Python expression and substitutes in place the result, transformed into a string. You can also ...