Heads or Tails?

I made this to see if I could create a random enough feeling with the use of some fairly simple rewrite rules.

Please note this is a Python script that is meant to be run in a command line, it's not really what you'd call a game but I'm curious about the implementation of the calculation of the result.

I guess in a sense that you could argue that I've created a pseudo random number generation algorithm by implementing it this way but it would be interesting to hear your thoughts on that.