sys:

Introduction: it mainly includes functions related to the interaction between python compiler and system.

Common functions:

import sys

print(sys.argv)#Name of this file,Parameters when the program is already running
#[As in the command window python3 mysys.py Parameter 1 Parameter 2]
#Then parameter 1 is sys.argv[1],And so on

print(sys.version)#python Version number
print(sys.path)#Returns the search path of the module, which is used during initialization PYTHONPATH Value of environment variable
# sys.exit(0)#Quit the program midway. When the parameter is not 0, a SystemExit exception will be thrown

sys.stdout.write()#Print on screen
sys.stdout.flush()#Refresh standard buffer

os:

Introduction: This module provides a convenient way to use operating system functions.

Common functions:

import os
print("-------getcwd()Get current directory-------")
print(os.getcwd())
print("-------chdir()Change the current directory-------")
# print(os.chdir("c://users"))#c:\\users   r'c:\users'
# print(os.getcwd())
print("------ . .. --------")
print(os.curdir)     #Print out .
print(os.pardir)     #Print out ..
print("-------makedirs Create directory recursively-------")
#os.makedirs(r"c:\a\b\c")     #To create c, create a if a does not exist, and b if b does not exist
print("-----remodir Delete directory recursively---------")
#os.removedirs(r"c:\a\b\c")    #Clear the empty folder from c to A. if a and B are also empty, they will also be deleted.
print("------mkdir Create directory--------")
# os.mkdir('c://a')
print("--------listdir Lists all files and subdirectories in the specified directory------")
print(os.listdir())
print("--------remove Delete files------")
# print(os.remove('c://newfile'))
print("-------rename File rename-------")
# os.rename('oldname','newname')
print("-------stat Get file or directory information-------")
print(os.stat('.'))
print("------sep Path dividers for output operating system characteristics--------")
print(os.sep)
print("-----linesep Output line terminator of current platform---------")
list1=[]
list1.append(os.linesep)
print(list1)
print("------pathsep Output the string used to split the file--------")
print(os.pathsep)
print("----------name Output operation platform----------")
# print(os.name)#nt
print("-------system implement shell command-------------")
print(os.system("dir"))
print("----------path About file and directory operations----------")
# print(os.path.abspath(__file__))###Return to absolute path
print(os.path.split(os.path.abspath(__file__)))##Cut paths into directory and file names
print(os.path.dirname(os.path.abspath(__file__)))#Take pathname only
print(os.path.dirname(__file__))###__file? Includes the full path name and also the absolute path
print(os.path.basename(__file__))#File name only
print(os.path.exists("c://a"))#Determine whether the path exists, regardless of directory or file
print(os.path.isabs(__file__))#Determine whether it is an absolute path
print(os.path.isfile("c://amd"))#Determine whether it is a document

print(os.path.join(r'c:',r'\a.txt'))#Combined absolute path

print("----------environ Get all environment variables of the current system----------")
print(os.environ)

print("---------popen() Method to open a pipe from a command-----------")
print(os.popen('dir').read())##Mainly used to process the return results of executing commands

print("Get process number".center(50,'-'))
print(os.getpid())#Get current process number
print(os.getppid())#Get parent process number

Be careful:

In some systems, the main difference between os.system and os.popen is that the return value of the former is the exit status code of the script, and the return value of the latter is a file descriptor storing the output content during the execution of the script.

time:

Introduction: contains functions about time

Common functions:

import time
print("--------time stamp-------------")
print("time stamp time:",time.time())#time stamp time: 1516435471.756463

print("----------Structured time(tm_year=2018, tm_mon=1.....-----------")
print("struct_time:",time.gmtime(time.time()))#tm_year=2018, tm_mon=1.........
print("timestamp->struct_time:",time.gmtime())#UTC time
print("local_time:",time.localtime())#Local time zone time


print("struct_time->timstamp:",time.mktime(time.gmtime()))#Structured time-->time stamp

print("----------ctime,asctime--------")
print("string_time:",time.ctime())###String time mon Feb 5 01:02:06 2018
print("asctime:",time.asctime())###String time mon Feb 5 01:02:06 2018


print("----------format_time Format time struct_time-----------")
#Structured time to format time:%Y representative year，%m representative month,%d representative day, %H representative hour，%M representative minute,%S representative second
#Will only replace%Y Equal characters do not replace characters without corresponding meaning
print("struct_time -> format_time:\n",  time.strftime("%Y-%m-%d %H:%M:%S",time.localtime()))
y=time.strftime("%Y-%m-%d %H:%M:%S",time.localtime())

#Format time to structure time
print("format_time -> struct_time:\n",time.strptime(y,"%Y-%m-%d %H:%M:%S"))

print("------------year--------------")
print("year:",time.localtime().tm_year)

random:

Introduction: store functions about "random"

Common functions:

import random
print("---------0 To 1,Random floating point value-----------")
print(random.random())
print("------------Random value from range,1<=x<=2--------")
print(random.randint(1,2))
print("------------Random value from the specified range--------")
print(random.randrange(1,3))
print("------------From a sequence, random values--------")
print(random.choice("hello"))#Random value from sequence
print(random.choice([0,11,3,99]))
print("------------From the sequence, randomly take the specified value--------")
print(random.sample('heigo',2))#
print("------------Random floating point value, start,end--------")
print(random.uniform(1,2))#start,end
print("-------Shuffle the cards,Disorder sorting-----")
l=[0,3,4,5,67,9]
random.shuffle(l)
print(l)