The difference between OS and sys two modules in Python
os and sys modules in python
The official explanations of the OS and SYS modules of the reproduced article are as follows:
Os: this module provides a portable the by using operating system dependent functionality.
This module provides a convenient way to use the operating system functions.
Sys: this module provides access to some variables used or maintained by the interpreter and to functions that interact St Rongly with the interpreter.
This module allows access to variables used or maintained by the interpreter and functions that interact with the interpreter.
The summary is that the OS module is responsible for interacting with the operating system, providing access to the underlying interface of the operating system, and the SYS module is responsible for the interaction between the program and the Python interpreter, providing a series of functions and variables for manipulating the Python runtime environment.
Os Common methods
Os.remove (‘ path/filename ‘) Delete file
Os.rename (Oldname, newname) renaming files
Os.walk () Generate all file names under the directory tree
Os.chdir (‘ dirname ‘) Change directory
Os.mkdir/makedirs (‘ dirname ‘) create a directory/multi-level directory
Os.rmdir/removedirs (‘ dirname ‘) Delete directory/multi-level directory
Os.listdir (‘ dirname ‘) lists the files for the specified directory
OS.GETCWD () Get the current working directory
Os.chmod () Changing directory permissions
Os.path.basename (‘ path/filename ‘) remove directory path, return file name
Os.path.dirname (‘ path/filename ‘) remove file name, return directory path
Os.path.join (path1[,path2[,…]]) combines the parts of the separation into one path name
Os.path.split (‘ path ‘) returns (DirName (), basename ()) tuple
Os.path.splitext () return (filename, extension) tuple
Os.path.getatime\ctime\mtime returns the last access, creation, modification time, respectively
Os.path.getsize () returns the file size
Os.path.exists () is present
Os.path.isabs () is an absolute path
Os.path.isdir () is a directory
Os.path.isfile () is a file
SYS Common Methods
SYS.ARGV command line argument list, the first element is the path of the program itself
Sys.modules.keys () returns the list of all modules that have been imported
Sys.exc_info () Gets the exception class currently being processed, Exc_type, Exc_value, exc_traceback the exception details currently handled
Sys.exit (n) exit program, Exit normally (0)
Sys.hexversion gets the version value of the Python interpreter, 16 binary format such as: 0x020403f0
Sys.version get version information for Python interpreter
Sys.maxint the largest int value
Sys.maxunicode the largest Unicode value
Sys.modules returns the module field of the system import, key is the module name, value is the module
Sys.path returns the search path for the module, using the value of the PYTHONPATH environment variable when initializing
Sys.platform returns the operating system platform name
Sys.stdout Standard Output
Sys.stdin Standard input
Sys.stderr Error Output
Sys.exc_clear () to clear current or recent error messages that are present on the current thread
Sys.exec_prefix returns the location of the platform standalone Python file installation
Sys.byteorder The local byte rule indicator, the value of the Big-endian platform is ‘ big ‘, the value of the Little-endian platform is ‘ little ‘
Sys.copyright record python copyright-related things
API version of C for the Sys.api_version interpreter
Sys.stdin,sys.stdout,sys.stderr
stdin, stdout, and stderr variables contain stream objects that correspond to standard I/O streams. If you need more control over the output, and print does not meet your requirements, they are what you need. You can also replace them, so you can redirect output and input to other devices, or handle them in a non-standard way.We often use print and raw_input to input and print, then How does print and raw_input relate to standard input/output streams?
In fact, the Python program’s standard input/output/error stream is defined in the SYS module, respectively: Sys.stdin,sys.stdout, Sys.stderr
The following programs can also be used to input and output the same:
import sys
sys.stdout.write(‘HelloWorld!‘)
print ‘Please enter yourname:‘,
name=sys.stdin.readline()[:-1]
print ‘Hi, %s!‘ % name
So Sys.stdin, Sys.stdout, stderr exactly what is it? We enter the following code in the Python Runtime environment:
import sys
for f in (sys.stdin,sys.stdout, sys.stderr): print f
output：
<open file‘<stdin>‘, mode ‘r‘ at 892210>
<open file‘<stdout>‘, mode ‘w‘ at 892270>
<open file‘<stderr>‘, mode ‘w at 8922d0>
It can be seen that stdin, stdout, stderr in Python are nothing more than file attributes, they are automatically associated with the standard input, output, and error in the shell environment when Python starts.
The I/O redirection of the Python program in the shell is exactly the same as the DOS command at the beginning of this article, which is actually provided by the shell and is not related to python itself. So can we redirect Stdin,stdout,stderr Read and write operations to an internal object inside a python program? The answer is yes.
Python provides a Stringio module to complete this idea, such as:
From Stringio import Stringio
Import Sys
Buff =stringio ()
Temp =sys.stdout #Save standard I/o Flow
Sys.stdout =buff #Redirect the standard I/o flow to Buff object
Print, ‘hello’, 0.001
Sys.stdout=temp #Restore standard I/O Flow
