Every major library or application I write seems to have a module named “util” these days.* I think it represents a kind of “impedance mismatch” between the platform I’m using (C runtime, C++ runtime, python standard libraries) and the platform I *wish* I were using.

Recently, I’ve been writing python code that runs lots of little UNIX utilities.* You know, like: find, ls, chmod, etc, etc.* It’s the kind of code that might also be written as a shell script, but python is much nicer when the program gets larger than about a page.* If you’re running lots of utilities, you want a variety of ways to interact with them.

Sometimes, you don’t want to send it any input, sometimes you do, sometimes you are expecting one line of output.* Sometimes you’re expecting a list of lines.* Sometimes you’re going to check the return code, sometimes you’re not.* These functions are all just small wrappers around calls to the python subprocess module in python.* But if you’re writing a lot of code that uses them, it’s important to make that code readable, so you want to streamline away most of the goop for dealing with the subprocess module.

I have utility routines for creating temporary files and removing them all when the program exits. There are routines to keep me from adding a lot of obscure import statements to the top of most of my modules.

Here’s some examples of what I’m using for now:

def gethostname():** from socket import gethostname** return gethostname()def timestamp():** import datetime** return str(datetime.datetime.today())Here’s a recipe that I got from stackoverflow.com.* I wanted the equivalent of “mkdir -p”, and you need a few lines to do that in python.

def mkdir_p(dir):* import errno* try:* * os.makedirs(dir)* except OSError, exc:* * if exc.errno == errno.EEXIST:** ** pass* * else:** ** raiseThere’s also code to do things that I’m convinced must have a better answer in python, but I haven’t found it yet.* So I isolate the hack to the until module.

def is_executable(file):* S_IEXEC = 00100* mode = os.stat(file).st_mode* return mode & S_IEXECMoving code in and out of my util module also prevents me from worrying so much about obscure modularity issues. Any code I don’t want to worry about today goes into the util module. When I know where it belongs, I can easily move it later. Of course, that’s much easier to do with python than in a language that uses header files like C or C++.

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