Posted Wednesday, June 13th, 2007 at 10:53 pm under python, tech.

resorting to regular expressions

I was going to write a much longer set of thoughts on moving to Python, but I don’t have time. Instead I’ll summarize by saying that I programmed for 28 years in various languages before switching to Python nearly 2 years ago.

I like Python. A lot. And there are multiple reasons, which I may go into another time.

One thing that has struck me as very interesting is my use of regular expressions. I came to Python after doing a lot of work in Perl (about 8 years). In Perl I used regular expressions all the time. And I mean every single day, many times a day. I like regular expressions. I understand pretty well how they work. I found multiple errors in the 2nd edition of Mastering Regular Expressions. I made a 20% speedup to version 4.72 of Grepmail with a trivial change to a regex. I put both GNU and Henry Spencer regex support into strsed. I use them in emacs lisp programming and in general day-to-day emacs usage, and in their limited form on the shell command line and in grep.

So given that regular expressions are so powerful, that I well know how to wield them, and that I did so perhaps ten thousand times during those 8 years of Perl, you might expect that I’d use them frequently in Python.

But that’s not the case.

In two years of writing Python almost every day, I think I’ve probably only used regular expressions about 10 times!

I’m not going to speculate now on why that might be the case. I’m writing this partly to see if others (in my huge circle of readers) have experienced something similar. I was prompted to write by an svn check in message of Daniel’s last night. He said:

You know things are bad when you find yourself resorting to regular expressions

And I knew exactly what he meant. When I find myself reaching for the Python pocket guide to refresh my memory on using Python regular expressions, it’s such an unusual event (especially given the contrast mentioned above) that I find myself wondering if maybe I’m doing something really inefficient and unPythonic.

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