in reply to
Formatting Strings Without Interpolating Whitespace
Why not use one of the many templating modules? I like Template Toolkit at lot, but it may be overkill for a simple application. On the other hand, "simple" applications tend to grow over time and then you are happy to have a full fledged templating engine on board.
A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James