Summing Up

Every regular expressions is actually a little program: a piece of data that tells a computer how to behave. The steps the computer goes through when executing a Python or Fortran program are more complicated than the ones it uses to compile and apply a regular expression, but the principles are exactly the same.

One last point to take away from this chapter is that if we know we are going to use regular expressions to read in data, we should choose a format for that data that’s easy for regular expressions to match. Optional commas, tabs that might be repeated, and other things that make data easy for people to type in actually make it harder for programs to read that data reliably. This tension between what’s easy for the machine and what’s easy for the user never goes away, but if we’re conscious of it, we can find a happy medium.