The sys module provides access to some
objects used or maintained by the interpreter and to functions that
interact strongly with the interpreter.
The sys module also provides the three
standard files used by Python.
-
sys.stdin
-
Standard input file object; used by
raw_input and input.
Also available via sys.stdin.read() and related
methods of the file object.
-
sys.stdout
-
Standard output file object; used by the
print
statement. Also available via
sys.stdout.write() and related methods of the file
object.
-
sys.stderr
-
Standard error object; used for error messages, typically
unhandled exceptions. Available via
sys.stderr.write() and related methods of the file
object.
A program can assign another file object to one of these global
variables. When you change the file for these globals, this will
redirect all of the interpreter's I/O.
One important object made available by this module is the variable
sys.argv. This variable has the command line
arguments used to run this script. For example, if we had a python
script called portfolio.py, and executed it with the following
command:
python portfolio.py -xvb display.csv
Then the sys.argv list
would be ["portfolio.py", "-xvb", "display.csv"].
Sophisticated argument processing is done with the
getopt or optparse
modules.
A few other interesting objects in the sys
module are the following variables.
-
sys.version
-
The version of this interpreter as a
string. For example, '2.5.1
(r251:54863, Apr 18 2007, 08:51:08) [MSC v.1310 32 bit
(Intel)]'
-
sys.version_info
-
Version information as a tuple, for
example: (2, 5, 1, 'final', 0).
-
sys.hexversion
-
Version information encoded as a single integer. Evaluating
hex(sys.hexversion) yields
'0x20501f0'.
-
sys.copyright
-
Copyright notice pertaining to this interpreter.
-
sys.platform
-
Platform identifier, for example,
'darwin', 'win32' or
'linux2'.
-
sys.prefix
-
Prefix used to find the Python library, for example
'/usr',
'/Library/Frameworks/Python.framework/Versions/2.5',
'c:\\Python25'.
