psi /

Filename Size Date modified Message
140 B
Deal with processes re-writing their argv wrongly
206 B
Merge another old head
4.3 KB
Use NoSuchProcessError instead of ValueError where appropriate
1.2 KB
Commit development brach splitting off python code from system data
192 B
Include the MANIFEST file so that can create other built
7.7 KB
Minor example update
2.9 KB
Update TODO
22.0 KB
Use the PyCapsule API on 2.7 and 3.1+

PSI - Python System Information

PSI is a Python package providing real-time access to processes and other miscellaneous system information such as architecture, boottime and filesystems. It has a pythonic API which is consistent accross all supported platforms but also exposes platform-specific details where desirable.


You need to check if it's supported on your platform, check the docstring of for the exact supported platforms.

You will also need a working C compiler and the python development files. If a system is not supported yet the build will fail. After building it is best to run the test suite, on some platforms not all tests might pass yet and you would rather know of these problems before starting to use PSI.

So to fully install PSI from source:

$ python build
$ python test
$ python install [<your options>]

See the Python documentation on installing Python module for more control:

Here a rough list of packages you will need for some popular GNU/Linux distributions, this should give you an idea of what is needed.


  • python
  • python-dev
  • gcc


  • python
  • python-devel
  • gcc



The argv array is read from the process memory on Solaris. If you do not have permissions to do this only the command and argc attributes of psi.process.Process will be available and using the args attribute will return the appropriate AttributeError.

Unit Tests

To run the unit tests:

$ python test

Some tests require superuser privileges and will be silently skipped when not running as root. This is required to run test applications with specific schedulers and priorities.

If any tests fail, please copy & paste the output and send operating system version, python version, python executable format (32/64-bit) and any other applicable details to the mailing list (


Examples are the best documentation. :-)

Python 2.5.2 (r252:60911, Oct  5 2008, 19:24:49)
[GCC 4.3.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import psi, psi.arch, psi.process
>>> a = psi.arch.arch_type()
>>> a
>>> isinstance(a, psi.arch.ArchLinux)
>>> isinstance(a, psi.arch.ArchSunOS)
>>> a.sysname
>>> a.nodename
>>> a.release
>>> a.release_info
(2L, 6L, 26L)
>>> a.version
'#1 SMP Thu Nov 20 21:57:00 UTC 2008'
>>> a.machine
>>> psi.loadavg()
(0.059999999999999998, 0.13, 0.13)
>>> import os
>>> mypid = os.getpid()
>>> mypid
>>> p = psi.process.Process(mypid)
>>> p.args
>>> p.exe
>>> p.uid
>>> import pwd
>>> pwd.getpwuid(p.uid)
pwd.struct_passwd(pw_name='flub', pw_passwd='x', pw_uid=1000,
pw_gid=1000, pw_gecos='Floris Bruynooghe,,,', pw_dir='/home/flub',
>>> p.start_time
datetime.datetime(2009, 5, 11, 20, 4, 31, 709993)
>>> help(psi.process.Process.start_time)
Help on getset descriptor psi.process.Process.start_time:

  Start time of process as datetime.datetime object

  Use .strftime('%s') to get seconds since epoch
>>> p.ppid
>>> parent = psi.process.Process(pid=p.ppid)
>>> parent.args
>>> p.rss
>>> pt = psi.process.ProcessTable()
>>> len(pt)
>>> pt.keys()
[1L, 2L, 3L, 4L, 5L, 6L, 7L, 6152L, 5660L, 6687L, 4648L, 5674L,
5639L, 6834L, 46L, 48L, 50L, 51L, 5684L, 1081L, 2621L, 5184L, 6276L,
2627L, 6217L, 6220L, 6221L, 4877L, 6224L, 6227L, 6229L, 6235L,
6757L, 5729L, 6244L, 2149L, 6246L, 2152L, 2153L, 6763L, 6764L,
6254L, 6248L, 6259L, 5749L, 2166L, 6249L, 2169L, 5242L, 2683L,
6781L, 6273L, 6274L, 4740L, 6278L, 6279L, 5772L, 5776L, 6290L,
5779L, 5268L, 6296L, 6809L, 156L, 157L, 158L, 6341L, 6307L, 2212L,
6257L, 20654L, 6856L, 4786L, 4788L, 5814L, 5817L, 6263L, 5821L,
6261L, 6336L, 4811L, 118L, 200L, 1739L, 5837L, 1742L, 1743L, 6349L,
20693L, 6265L, 5852L, 122L, 4833L, 4834L, 1253L, 2793L, 1258L,
6382L, 21374L, 6393L, 5885L, 1278L, 5376L, 6401L, 5675L, 1290L,
1293L, 6445L, 5397L, 6262L, 5913L, 4385L, 4386L, 4392L, 4393L,
4394L, 1074L, 6449L, 5426L, 6456L, 6458L, 5951L, 19779L, 5963L,
5964L, 21327L, 21304L, 5466L, 4955L, 4444L, 2404L, 5501L, 6526L,
4992L, 4993L, 6032L, 6572L, 6442L, 5573L, 5576L, 2794L, 17357L,
4054L, 6397L, 6136L]
>>> q = pt[6856]
>>> q.args
>>> q.env
{'GNOME_DESKTOP_SESSION_ID': 'this-is-deprecated', 'LOGNAME':
'flub', 'USER': 'flub', 'HOME': '/home/flub', 'PATH':
'DISPLAY': ':0.0', 'SSH_AGENT_PID': '6217', 'LANG': 'en_GB.UTF-8',
'SHELL': '/bin/bash', 'XDG_SESSION_COOKIE':
'SESSION_MANAGER': 'local/signy:/tmp/.ICE-unix/6152',
'XDG_DATA_DIRS': '/usr/local/share/:/usr/share/:/usr/share/gdm/',
'/tmp/seahorse-SWS6qW/S.gpg-agent:6235:1', 'USERNAME': 'flub',
'/tmp/keyring-AStyaD/ssh', 'DESKTOP_SESSION': 'gnome', 'GDMSESSION':
'ORBIT_SOCKETDIR': '/tmp/orbit-flub', 'XAUTHORITY':
'/home/flub/.Xauthority', 'GNOME_KEYRING_SOCKET':
'/tmp/keyring-AStyaD/socket', 'GNOME_KEYRING_PID': '6246\n',
'GDM_LANG': 'en_GB.UTF-8', 'PWD': '/home/flub', 'GTK_RC_FILES':
>>> r = []
>>> for pp in pt.values():
...     if pp.args and 'evolution' in pp.args[0]:
...         r.append(pp)
>>> r
[psi.process.Process(pid=6336), psi.process.Process(pid=6572),
>>> for pp in r:
...     print ' '.join(pp.args)
/usr/lib/evolution/2.24/evolution-exchange-storage --oaf-activate-iid=OAFIID:GNOME_Evolution_Exchange_Connector_CalFactory:1.2 --oaf-ior-fd=22
/usr/lib/evolution/evolution-data-server-2.24 --oaf-activate-iid=OAFIID:GNOME_Evolution_DataServer_CalFactory:1.2 --oaf-ior-fd=23
>>> init = psi.process.Process(1)
>>> init.env
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
psi.InsufficientPrivsError: Insufficient privileges for Process.env

Some sample scripts are also available in the examples/ subdirectory.


You should definitely read the DESIGN file, it will explain the ideas behind how the code is structured and how you should extend it. Also very useful is the TODO file and the wiki (

The has some extra features that help with development, these are explained in its docstring.

The PSI source code is hosted at bitbucket in a Mercurial repository,


If PSI does not yet work on your architecture/system then it needs to be ported, the design is aimed at making this easy for you. There is no separate porting guide at the moment so you will have to read the DESIGN file for details of what to do.


There is a mailing list at where you can post questions, patches, hints, bugs, etc. Your feedback is welcome!