Scott Leberknight's Weblog

Yesterday I completed my very first real, though very novice, Python script at work. We were creating a "commons" project for several projects past and present that I am working on that combines utility classes created over the pasts few years. We merged the codebase from the projects and needed to go through all the Java source files and modify headers, Javadoc tags, and footers to be consistent. I wrote a relatively short Python script to do this, and found it was pretty easy. Despite the fact that I have barely started to learn Python I was able to use the os module to work with files and directories, and to use the re module to use regular expressions to match various strings.

Definitely the coolest thing was the walk() function which (from the Python documentation) "generates the file names in a directory tree, by walking the tree either top down or bottom up. For each directory in the tree rooted at directory top (including top itself), it yields a 3-tuple (dirpath, dirnames, filenames)." For example, suppose you wanted to find all Windows .bat files starting from the c:\projects directory. The following script does just that. I am sure an expert Python developer could do it in fewer lines, but I am just starting out with Python so I'm sure it's not the best code.

import os
import re

for root, dirs, files in os.walk('c:\projects', topdown=False):
  for file in files:
    match = re.compile('.*bat$').match(file)
    if match != None:
      print 'Found file: ' + file + ' in dir ' + root


Pretty cool. I am not even going to bother seeing how many more lines of Java code this would take, but I'm sure it would be a lot more. Anyway, the way the walk() method returns a "3-tuple" is just plain cool, and it's even cooler how you can just define them in the for loop. I definitely plan to continue learning Python and keep this snake in my software tool garden. Ok, I cannot believe I just wrote that. Must be getting old if the cheesy and sucky jokes are starting already.