Python: Python: OS module

Snipplr-25249.py

# The os module provides a portable platform-independent interface to access common operating services,
# allowing you to add OS-level support to your programs.

# The os.path.abspath(path) function of the os module returns a string version of the absolute path of the
# path specified. Because abspath takes into account the current working directory, the . and .. directory
# options will work as shown next:

>>>print os.path.abspath(".") 
>>>C:\books\python\ch1\ print os.path.abspath("..") C:\books\python\

## The os.path module provides the exists(path), isdir(path), and isfile(path) function to check for the
# existence of files and directories, as shown here:

>>>print os.path.exists("/books/python/ch1") 
True 
>>>print os.path.isdir("/books/python/ch1") 
True 
>>>print
os.path.isfile("/books/python/ch1/ch1.doc") 
True

## The os.chdir(path) function provides a simple way of changing the current working directory for the program,
# as follows:

>>>os.chdir("/books/python/ch1/code") 
>>>print os.path.abspath(".") 
C:\books\python\CH1\code

## The os.environ attribute contains a dictionary of environmental variables. You can use this dictionary as
# shown next to access the environmental variables of the system:

>>>print os.environ['PATH'] 
C:\WINNT\system32;C:\WINNT;C:\Python24

## The os.system(command) function will execute a system function as if it were in a subshell, as shown with
# the following dir command:

>>>os.system("dir") 
Volume Serial Number is 98F3-A875
 Directory of C:\books\python\ch1\code
08/11/2006  02:10p      <DIR>          .
08/11/2006  02:10p      <DIR>          ..
08/10/2006  04:00p                 405 format.py
08/10/2006  10:27a                 546 function.py
08/10/2006  03:07p                 737 scope.py
08/11/2006  02:58p                 791 sys_tools.py
               4 File(s)          3,717 bytes
               2 Dir(s)   7,880,230,400 bytes free

## Python provides a number of exec type functions to execute applications on the native system. The following
# example illustrates using the os.execvp(path, args) function to execute the application update.exe with a
# command-line parameter of -verbose:

>>>os.execvp("update.exe", ["-verbose"])