import sh

2014-06-02 | python

A small python library which seems to work rather well when it comes to shelling out is sh. It provides a handy and lightweight abstraction above the means already available within python.

The features I found most useful:

easily check for program availability: I prefer to "instantiate" the programs I want to use within the first few moments of execution and in case a command is not available ... the script fails fast
it provides a nice abstraction around program execution and lets you chain shell commands together in a more pythonic way (could be interesting to combine it with something like the pipe module or with hy)
you can provide arguments to shell commands just as you would for ordinary functions
you can "bake" (prepare) commands and pass them around inside your program
you can take advantage of generators for stdout handling and you can background commands easily which is quite useful for wrapping longer running processes

Take the small script on this page for example. At the top of the script sh.py is being imported with import sh. Then further down, the following lines test for command availability and make the commands available as python objects.

    git = sh.git
    ls = sh.ls
    docker = sh.docker
    test = sh.test

In case the command in question does not exist, the library will throw an exception. This enables us to check the environment and bail out with a minimal amount of code.

Further down I can simply use this line

            digest = git('ls-remote', repo, 'refs/heads/master').split()[0]

to read out remote git repository information and work on the command's output right away with a small amount of code. Of course I could use the subprocess module too to achieve similar functionality but using sh tends to result in cleaner implementations and adds more flexibility.

It surely is worth a shot.