Introducing py-pkg: Python wrappers for libpkg

For the past few weeks I’ve been working on a Python project and since then I really enjoy using Python everyday.

Now is the time to actually present the project, so let me introduce to you py-pkg – Python wrappers for FreeBSD’s libpkg library.

Here I’ll just try to add a few lines about py-pkg and what is interesting about it. Then I’ll show you a few examples on how to use py-pkg in order to manage your FreeBSD package database!

General Information

Q: So, what is py-pkg?

The goal of py-pkg is to provide Python wrappers for FreeBSD’s libpkg library. The wrappers themself are written in Cython, which gives you the flexibility and power to use Python with C data structures, very neat! :)

The Python wrappers themself are being compiled as a shared library and can be imported into Python as any other Python module.

Q: So, what can I use py-pkg for?

You can do a lot with it, here are just a few examples:

Querying information about your packages
Searching remote repositories for packages
Install packages
Delete packages
Upgrade packages
etc, etc, etc.

Q: Yeah, I can do that with pkg(8) already, what’s the point of py-pkg?

The idea of py-pkg is to expose libpkg functionallity to Python in a way that pkg(8) already uses it.

Think about this for a second: what does it take to write a Gtk/Qt interface for libpkg in C and what does it take to do the same thing in Python? I’m sure you know the answer already.

So, by providing Python wrappers for libpkg, new doors open for you. Just think about it – new frontends, new plugins, etc. and all that you can do in Python! :)

Enough words already, time to go into the real deal.

Repository and documentation

You can find the source code repository for py-pkg on the link below:

py-pkg repository

And here you can find the py-pkg Sphinx documentation:

py-pkg Sphinx documentation

Requirements and installation of py-pkg

In order to install py-pkg you need to be running the development version of libpkg (e.g. the one from the master branch of pkgng).

Then in order to build the wrappers you would need to have lang/cython. Afterwards building and installing is pretty straight-forward:

$ python setup.py build
$ sudo python setup.py install

Okay, lets go and check some examples now! :)

Examples

Here, I’ll add a few examples of using py-pkg on a FreeBSD system in order to manage the package database.

You can also find these and other examples at the example’s page at the Github repository.

So, read further, hope you enjoy it.

Querying the package database

Here is how you could list all installed packages on your FreeBSD system from Python and py-pkg:

#!/usr/bin/env python

import pkg

db = pkg.PkgDb()
pkgs = db.query()

for p in pkgs:
    print p

db.close()

Pretty easy, isn’t it? :)

Searching for packages on a remote repository

This is how you would search a remote repository for a package.

#!/usr/bin/env python
	
db = pkg.PkgDb(remotedb=True)

pkgs = db.rquery(pattern='zsh')

for p in pkgs:
    print p

db.close()

Installing packages

This is how you would install a package using Python and py-pkg:

First, let’s see how this can be done from an interactive Python session, and later you can find a simple script that you can use for the same purpose.

Let’s first start up our Python interpreter now:

% python
Python 2.7.5 (default, May 30 2013, 14:08:13) 
[GCC 4.2.1 20070831 patched [FreeBSD]] on freebsd9
Type "help", "copyright", "credits" or "license" for more information.
>>> 

First we are going to check whether the package we want is not installed already, and if not – we are going to install it.

>>> import pkg
>>> db = pkg.PkgDb()
>>> 'security/apg' in db.query()
False

Okay, that means that security/apg is not installed on our system, lets see if we have this package on our repository.

>>> 'security/apg' in db.rquery()
True

So, we’ve got security/apg in our remote repository, lets go ahead and install it:

>>> jobs = db.install(['apg'])
>>> jobs.apply()

Lets see if we have the package installed now:

>>> 'security/apg' in db.query()                                                                           
True

And we’ve got our package installed. Below is the short version for installing a package:

#!/usr/bin/env python

import pkg

db = pkg.PkgDb()
	
jobs = db.install(['apg'])
jobs.apply()
	
db.close()

What is your BSD license coverage?

Okay, here’s an interesting example, that will show you all the packages on your system which are BSD and MIT licensed.

#!/usr/bin/env python
	
import pkg
		
db = pkg.PkgDb()
	
pkgs = db.query()
pkgs.load_licenses()
	
for p in pkgs:
    for license in ['BSD', 'MIT']:
        if license in p.licenses():
            print '%s is %s licensed' % (p.origin(), license)
				
db.close()

What repositories do I have?

Here’s how you could list your package repositories.

#!/usr/bin/env python

import pkg

db = pkg.PkgDb()

for repo in db.repositories():
    print '%s: %s [enabled: %s]' % (repo.name(), repo.url(), repo.enabled())

db.close()

Here’s an example output of the above script:

repo-packagesite: file:///home/dnaeon/PROJECTS/pkg-repo [enabled: True]

Checking for missing package dependencies

Here’s a simply Python script that can detect missing dependencies in your package database.

#!/usr/bin/env python

from pkg import *

def check_deps(pkg, db):
    for dep in pkg.deps():
        if not db.pkg_is_installed(dep.origin()):
            print '%s has a missing dependency: %s' % (pkg.origin(), dep.origin())

def main():
    db = PkgDb()

    pkgs = db.query()
    pkgs.load_deps()
		
    for pkg in pkgs:
        check_deps(pkg, db)

    db.close()

if __name__ == '__main__':
    main()

Written on June 5, 2013