Python Tutorials - Herong's Tutorial Examples - v2.14, by Herong Yang
What Is "sys" Module
This section describes the 'sys' module, which allows you to access information from the Python system that executes the Python script.
What Is "sys" Module? "sys" is a Python module that allows you to access information from the Python system that executes the Python script.
Some commonly used properties and methods of the "sys" module are:
1. sys.argv - Property holds a list of command line arguments used to invoke this Python script. sys.argv[0] is the Python script file path. Below is an example on how to use sys.argv:
herong$ more argv_echoer.py
import sys
for i in range(len(sys.argv)):
print("argv["+str(i)+"] = "+sys.argv[i])
herong$ python argv_echoer.py say "good morning"
argv[0] = argv_echoer.py
argv[1] = say
argv[2] = good morning
2. sys.copyright - Property holds the copyright information of the Python system.
>>> import sys >>> print(sys.copyright) Copyright (c) 2001-2019 Python Software Foundation. All Rights Reserved. Copyright (c) 2000 BeOpen.com. All Rights Reserved. Copyright (c) 1995-2001 Corporation for National Research Initiatives. All Rights Reserved. Copyright (c) 1991-1995 Stichting Mathematisch Centrum, Amsterdam. All Rights Reserved.
3. sys.executable - Property holds the executable program that launches the Python system.
>>> sys.executable '/Library/Frameworks/Python.framework/Versions/3.8/bin/python3'
4. sys.getdefaultencoding() - Method returns the default encoding of characters.
>>> sys.getdefaultencoding() 'utf-8'
5. sys.getrefcount(object) - Method returns the numbers of references on the given object. The code below shows that a string literal has 3 references. I am not sure why.
>>> sys.getrefcount("Hello")
3
>>> msg = "Hello"
>>> sys.getrefcount(msg)
2
>>> ref = msg
>>> sys.getrefcount(ref)
3
6. sys.getsizeof(object) - Method returns the storage size of the given object. The code below shows that a string object has 49 bytes of overhead.
>>> msg = "Hello" >>> sys.getsizeof(msg) 54 >>> len(msg) 5 >>> msg = "Hello Joe!" >>> sys.getsizeof(msg) 59 >>> len(msg) 10
7. sys.modules - Property holds a dictionary of available modules.
>>> sys.modules.keys() dict_keys(['sys', 'builtins', '_frozen_importlib', '_imp', '_warnings', ... ...
8. sys.path - Property holds a dictionary of available modules.
>>> sys.path ['', '/usr/local/anaconda3/lib/python39.zip', '/usr/local/anaconda3/lib/python3.9', '/usr/local/anaconda3/lib/python3.9/lib-dynload', '/usr/local/anaconda3/lib/python3.9/site-packages' ]
9. sys.platform - Property holds the platform name of the operating system.
>>> sys.platform 'linux'
10. sys.stdin, sys.stdout, and sys.stderr - Properties hold file handles for input, output and error processing.
>>> res = sys.stdout.write("Hello\n")
Hello
11. sys.version - Properties holds the version number of the Python system.
>>> sys.version '3.9.12 (main, Apr 5 2022, 06:56:58) \n[GCC 7.5.0]'
Table of Contents
Variables, Operations and Expressions
Function Statement and Function Call
Iterators, Generators and List Comprehensions
Packages and Package Directories
Use "os" Module to Create Child Processes
Use "os" Module to Manage Files
"pathlib" - Object-Oriented Filesystem Paths
"pip" - Package Installer for Python
SciPy.org - Python Libraries for Science
pandas - Data Analysis and Manipulation
Anaconda - Python Environment Manager