Shulou(Shulou.com)06/03 Report--

This article focuses on "how to understand the python os.system implementation of cmd instruction code", interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn "how to understand the code of python os.system executing cmd instructions".

1. Execute the cmd instruction, and the output in cmd will be output directly on the console. A result of 0 indicates that the execution is successful.

2. After calling the shell script, a 16-bit binary number is returned. The low bit is the signal number that kills the called script, and the high bit is the exit status code of the script.

The os.system () method simply executes the cmd instruction rudely, and there is no way to get the contents of the cmd output.

Example # coding:utf-8import osos.system ("ls") Python how to use the OS module to call cmd

Two methods to call cmd, os.popen () and os.system (), are provided in the os module

Os.system (cmd) requires a terminal to be opened when executing the command command, and the execution result of the command command cannot be saved.

Os.popen (cmd,mode) opens a pipe with the command process. The return value is a file object that can be read or written (determined by mode, default is'r'). If mode is' ringing, you can call read () with the return value of this function to get the execution result of the command command.

Os.system ()

Definition:

Def system (* args, * * kwargs): # real signature unknown "" Execute the command in a subshell. "" Pass

To put it simply, execute the command command in shell

Example:

(venv) C:\ Users\ TynamYang > pythonPython 3.7.0 (v3.7.0:1bf9cc5093, Jun 27 2018, 04:06:47) [MSC v.1914 32 bit (Intel)] on win32Type "help", "copyright", "credits" or "license" for more information. > import os > > cmd = 'echo "I am tynam' > > os.system (cmd)" I am tynam "> >

Os.popen ()

Definition:

# Supply os.popen () def popen (cmd, mode= "r", buffering=-1): if not isinstance (cmd, str): raise TypeError ("invalid cmd type (% s, expected string)"% type (cmd)) if mode not in ("r", "w"): raise ValueError ("invalid mode% r"% mode) if buffering= = 0 or buffering is None: raise ValueError ("popen () does not support unbuffered streams") import subprocess Io if mode = "r": proc = subprocess.Popen (cmd, shell=True, stdout=subprocess.PIPE, bufsize=buffering) return _ wrap_close (io.TextIOWrapper (proc.stdout), proc) else: proc = subprocess.Popen (cmd, shell=True, stdin=subprocess.PIPE, bufsize=buffering) return _ wrap_close (io.TextIOWrapper (proc.stdin) Proc)

The command command is also executed in shell, but the result returned is a file object that can be read and written to

Three of these parameters mean:

Command-shell command executed

Mode-Mode permission, read ('r') or write ('w'). Default is read ('r')

Bufsize-if the buffer value is set to 0, no buffering will occur. If the buffer value is 1, line buffering will be performed when the file is accessed. If the buffer value is set to an integer greater than 1, the buffer operation is performed at the set buffer size. If negative, the buffer size is the system default (default behavior).

Example:

> import os > cmd = 'echo "I am tynam' > f = os.popen (cmd,'r') > f.read ()'" I am tynam "\ n'> > at this point, I believe you have a deeper understanding of" how to understand the python os.system execution of cmd instruction code ". You might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.