How to write Python bindings for command line applications

Question

I'm interested in writing a python binding or wrapper for an existing command line utility that I use on Linux, so that I can access its features in my python programs. Is there a standard approach to doing this that someone could point me to?

At the moment, I have wrapped the command line executable in a subprocess.Popen call, which works but feels quite brittle, and I'd like to make the integration between the two sides much more stable so that it works in places other than my own computer!

There shouldn't be any problem with that method working on other computers, assuming that the utility is installed in the same place across computers. If not, then that's a problem that's out of the scope of Python bindings. — rossipedia
– rossipedia, Commented Nov 4, 2010 at 20:39

Mike Axiak · Accepted Answer · 2010-11-04 20:39:53Z

5

If you must use a command line interface, then subprocess.Popen is your best bet. Remember that you can use shell=True to let it pick the path variables, you can use os.path.join to use OS-dependent path separators etc.

If, however, your command line utility has shared libraries, look at ctypes, which allows you to connect directly to those libraries and expose functionality directly.

answered Nov 4, 2010 at 20:39

Mike Axiak

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pyfunc · Accepted Answer · 2010-11-04 20:41:44Z

1

One way would be to

re-factor your command line utility so that command line handling is separated and the actual functionality is exposed as shared archive.
Then you could expose those function using cython.
Write your complete command line utility in python that exploits those functions.

This makes distribution hard though.

What you are doing is still the best way.

answered Nov 4, 2010 at 20:41

pyfunc

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3 Comments

John La Rooy Over a year ago

You should first check that someone else hasn't already done some of those steps for you - particularly step 1

Richard J Over a year ago

Unfortunately the command line utility isn't mine, it's just one that I use a lot, and would like to use in my applications. I'd like to contribute a binding for Python if possible, but just not sure how to go about doing that in general.

pyfunc Over a year ago

@Richard J: Bindings are better created using the library approach. cython, ctypes etc. But you do not have access then you will have to rely on the approach used for external command execution - subprocess.Popen.

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