>>> import os
>>> print os.name
posix
>>> import platform
>>> platform.system()
'Linux'
>>> platform.release()
'2.6.22-15-generic'

The output of platform.system() is as follows:

• Linux: Linux
• Mac: Darwin
• Windows: Windows

See: platform — Access to underlying platform’s identifying data

Dang -- lbrandy beat me to the punch, but that doesn't mean I can't provide you with the system results for Vista!

>>> import os
>>> os.name
'nt'
>>> import platform
>>> platform.system()
'Windows'
>>> platform.release()
'Vista'

...and I can’t believe no one’s posted one for Windows 10 yet:

>>> import os
>>> os.name
'nt'
>>> import platform
>>> platform.system()
'Windows'
>>> platform.release()
'10'

For the record here's the results on Mac:

>>> import os
>>> os.name
'posix'
>>> import platform
>>> platform.system()
'Darwin'
>>> platform.release()
'8.11.1'

Sample code to differentiate OS's using python:

from sys import platform as _platform

if _platform == "linux" or _platform == "linux2":
   # linux
elif _platform == "darwin":
   # MAC OS X
elif _platform == "win32":
   # Windows
elif _platform == "win64":
    # Windows 64-bit

You can also use sys.platform if you already have imported sys and you don't want to import another module

>>> import sys
>>> sys.platform
'linux2'

If you want user readable data but still detailed, you can use platform.platform()

>>> import platform
>>> platform.platform()
'Linux-3.3.0-8.fc16.x86_64-x86_64-with-fedora-16-Verne'

Here's a few different possible calls you can make to identify where you are

import platform
import sys

def linux_distribution():
  try:
    return platform.linux_distribution()
  except:
    return "N/A"

print("""Python version: %s
dist: %s
linux_distribution: %s
system: %s
machine: %s
platform: %s
uname: %s
version: %s
mac_ver: %s
""" % (
sys.version.split('\n'),
str(platform.dist()),
linux_distribution(),
platform.system(),
platform.machine(),
platform.platform(),
platform.uname(),
platform.version(),
platform.mac_ver(),
))

The outputs of this script ran on a few different systems (Linux, Windows, Solaris, MacOS) and architectures (x86, x64, Itanium, power pc, sparc) is available here: https://github.com/hpcugent/easybuild/wiki/OS_flavor_name_version

Ubuntu 12.04 server for example gives:

Python version: ['2.6.5 (r265:79063, Oct  1 2012, 22:04:36) ', '[GCC 4.4.3]']
dist: ('Ubuntu', '10.04', 'lucid')
linux_distribution: ('Ubuntu', '10.04', 'lucid')
system: Linux
machine: x86_64
platform: Linux-2.6.32-32-server-x86_64-with-Ubuntu-10.04-lucid
uname: ('Linux', 'xxx', '2.6.32-32-server', '#62-Ubuntu SMP Wed Apr 20 22:07:43 UTC 2011', 'x86_64', '')
version: #62-Ubuntu SMP Wed Apr 20 22:07:43 UTC 2011
mac_ver: ('', ('', '', ''), '')

I do this

import sys
print sys.platform

Docs here : sys.platform.

Everything you need is probably in the sys module.

How about a new answer:

import psutil
psutil.MACOS   #True (OSX is deprecated)
psutil.WINDOWS #False
psutil.LINUX   #False 

This would be the output if I was using MACOS

I am using the WLST tool that comes with weblogic, and it doesn't implement the platform package.

wls:/offline> import os
wls:/offline> print os.name
java 
wls:/offline> import sys
wls:/offline> print sys.platform
'java1.5.0_11'

Apart from patching the system javaos.py (issue with os.system() on windows 2003 with jdk1.5) (which I can't do, I have to use weblogic out of the box), this is what I use:

def iswindows():
  os = java.lang.System.getProperty( "os.name" )
  return "win" in os.lower()

>>> import platform
>>> platform.system()

/usr/bin/python3.2

def cls():
    from subprocess import call
    from platform import system

    os = system()
    if os == 'Linux':
        call('clear', shell = True)
    elif os == 'Windows':
        call('cls', shell = True)

For Jython the only way to get os name I found is to check os.name Java property (tried with sys, os and platform modules for Jython 2.5.3 on WinXP):

def get_os_platform():
    """return platform name, but for Jython it uses os.name Java property"""
    ver = sys.platform.lower()
    if ver.startswith('java'):
        import java.lang
        ver = java.lang.System.getProperty("os.name").lower()
    print('platform: %s' % (ver))
    return ver

I started a bit more systematic listing of what values you can expect using the various modules (feel free to edit and add your system):

Linux (64bit) + WSL

os.name                     posix
sys.platform                linux
platform.system()           Linux
sysconfig.get_platform()    linux-x86_64
platform.machine()          x86_64
platform.architecture()     ('64bit', '')

• tried with archlinux and mint, got same results
• on python2 sys.platform is suffixed by kernel version, e.g. linux2, everything else stays identical
• same output on Windows Subsystem for Linux (tried with ubuntu 18.04 LTS), except platform.architecture() = ('64bit', 'ELF')

WINDOWS (64bit)

(with 32bit column running in the 32bit subsystem)

official python installer   64bit                     32bit
-------------------------   -----                     -----
os.name                     nt                        nt
sys.platform                win32                     win32
platform.system()           Windows                   Windows
sysconfig.get_platform()    win-amd64                 win32
platform.machine()          AMD64                     AMD64
platform.architecture()     ('64bit', 'WindowsPE')    ('64bit', 'WindowsPE')

msys2                       64bit                     32bit
-----                       -----                     -----
os.name                     posix                     posix
sys.platform                msys                      msys
platform.system()           MSYS_NT-10.0              MSYS_NT-10.0-WOW
sysconfig.get_platform()    msys-2.11.2-x86_64        msys-2.11.2-i686
platform.machine()          x86_64                    i686
platform.architecture()     ('64bit', 'WindowsPE')    ('32bit', 'WindowsPE')

msys2                       mingw-w64-x86_64-python3  mingw-w64-i686-python3
-----                       ------------------------  ----------------------
os.name                     nt                        nt
sys.platform                win32                     win32
platform.system()           Windows                   Windows
sysconfig.get_platform()    mingw                     mingw
platform.machine()          AMD64                     AMD64
platform.architecture()     ('64bit', 'WindowsPE')    ('32bit', 'WindowsPE')

cygwin                      64bit                     32bit
------                      -----                     -----
os.name                     posix                     posix
sys.platform                cygwin                    cygwin
platform.system()           CYGWIN_NT-10.0            CYGWIN_NT-10.0-WOW
sysconfig.get_platform()    cygwin-3.0.1-x86_64       cygwin-3.0.1-i686
platform.machine()          x86_64                    i686
platform.architecture()     ('64bit', 'WindowsPE')    ('32bit', 'WindowsPE')

Some remarks:

• there is also distutils.util.get_platform() which is identical to `sysconfig.get_platform
• anaconda on windows is same as official python windows installer
• I don't have a Mac nor a true 32bit system and was not motivated to do it online

To compare with your system, simply run this script (and please append results here if missing :)

from __future__ import print_function
import os
import sys
import platform
import sysconfig

print("os.name                      ",  os.name)
print("sys.platform                 ",  sys.platform)
print("platform.system()            ",  platform.system())
print("sysconfig.get_platform()     ",  sysconfig.get_platform())
print("platform.machine()           ",  platform.machine())
print("platform.architecture()      ",  platform.architecture())

Interesting results on windows 8:

>>> import os
>>> os.name
'nt'
>>> import platform
>>> platform.system()
'Windows'
>>> platform.release()
'post2008Server'

Edit: That's a bug

Watch out if you're on Windows with Cygwin where os.name is posix.

>>> import os, platform
>>> print os.name
posix
>>> print platform.system()
CYGWIN_NT-6.3-WOW

in the same vein....

import platform
is_windows=(platform.system().lower().find("win") > -1)

if(is_windows): lv_dll=LV_dll("my_so_dll.dll")
else:           lv_dll=LV_dll("./my_so_dll.so")

If you not looking for the kernel version etc, but looking for the linux distribution you may want to use the following

in python2.6+

>>> import platform
>>> print platform.linux_distribution()
('CentOS Linux', '6.0', 'Final')
>>> print platform.linux_distribution()[0]
CentOS Linux
>>> print platform.linux_distribution()[1]
6.0

in python2.4

>>> import platform
>>> print platform.dist()
('centos', '6.0', 'Final')
>>> print platform.dist()[0]
centos
>>> print platform.dist()[1]
6.0

Obviously, this will work only if you are running this on linux. If you want to have more generic script across platforms, you can mix this with code samples given in other answers.

try this:

import os

os.uname()

and you can make it :

info=os.uname()
info[0]
info[1]

Check the available tests with module platform and print the answer out for your system:

import platform

print dir(platform)

for x in dir(platform):
    if x[0].isalnum():
        try:
            result = getattr(platform, x)()
            print "platform."+x+": "+result
        except TypeError:
            continue

You can also use only platform module without importing os module to get all the information.

>>> import platform
>>> platform.os.name
'posix'
>>> platform.uname()
('Darwin', 'mainframe.local', '15.3.0', 'Darwin Kernel Version 15.3.0: Thu Dec 10 18:40:58 PST 2015; root:xnu-3248.30.4~1/RELEASE_X86_64', 'x86_64', 'i386')

A nice and tidy layout for reporting purpose can be achieved using this line:

for i in zip(['system','node','release','version','machine','processor'],platform.uname()):print i[0],':',i[1]

That gives this output:

system : Darwin
node : mainframe.local
release : 15.3.0
version : Darwin Kernel Version 15.3.0: Thu Dec 10 18:40:58 PST 2015; root:xnu-3248.30.4~1/RELEASE_X86_64
machine : x86_64
processor : i386

What is missing usually is the operating system version but you should know if you are running windows, linux or mac a platform indipendent way is to use this test:

In []: for i in [platform.linux_distribution(),platform.mac_ver(),platform.win32_ver()]:
   ....:     if i[0]:
   ....:         print 'Version: ',i[0]

If you are running macOS X and run platform.system() you get darwin because macOS X is built on Apple's Darwin OS. Darwin is the kernel of macOS X and is essentially macOS X without the GUI.

This solution works for both python and jython.

module os_identify.py:

import platform
import os

# This module contains functions to determine the basic type of
# OS we are running on.
# Contrary to the functions in the `os` and `platform` modules,
# these allow to identify the actual basic OS,
# no matter whether running on the `python` or `jython` interpreter.

def is_linux():
    try:
        platform.linux_distribution()
        return True
    except:
        return False

def is_windows():
    try:
        platform.win32_ver()
        return True
    except:
        return False

def is_mac():
    try:
        platform.mac_ver()
        return True
    except:
        return False

def name():
    if is_linux():
        return "Linux"
    elif is_windows():
        return "Windows"
    elif is_mac():
        return "Mac"
    else:
        return "<unknown>" 

Use like this:

import os_identify

print "My OS: " + os_identify.name()

import sys
import platform

# return a platform identifier
print(sys.platform)

# return system/os name
print(platform.system())

# print system info
# similar to 'uname' command in unix
print(platform.uname())

Use the import os and os.name keywords.

How about a simple Enum implementation like the following? No need for external libs!

import platform
from enum import Enum
class OS(Enum):
    def checkPlatform(osName):
        return osName.lower()== platform.system().lower()

    MAC = checkPlatform("darwin")
    LINUX = checkPlatform("linux")
    WINDOWS = checkPlatform("windows")  #I haven't test this one

Simply you can access with Enum value

if OS.LINUX.value:
    print("Cool it is Linux")

P.S It is python3

You can look at the code in pyOSinfo which is part of the pip-date package, to get the most relevant OS information, as seen from your Python distribution.

One of the most common reasons people want to check their OS is for terminal compatibility and if certain system commands are available. Unfortunately, the success of this checking is somewhat dependent on your python installation and OS. For example, uname is not available on most Windows python packages. The above python program will show you the output of the most commonly used built-in functions, already provided by os, sys, platform, site.

So the best way to get only the essential code is looking at that as an example. (I guess I could have just pasted it here, but that would not have been politically correct.)

I am late to the game but, just in case anybody needs it, this a function I use to make adjustments on my code so it runs on Windows, Linux and MacOs:

import sys
def get_os(osoptions={'linux':'linux','Windows':'win','macos':'darwin'}):
    '''
    get OS to allow code specifics
    '''   
    opsys = [k for k in osoptions.keys() if sys.platform.lower().find(osoptions[k].lower()) != -1]
    try:
        return opsys[0]
    except:
        return 'unknown_OS'