Python system programming (self-Learning Python series notes-3) (not regularly updated)

L If __name__ = = ' __main__ ': # when running as a script

n __name__ detection is only ture when the file is running , is false when it isloaded , and is determined when it isrun as a top-level script ture

N run: Command line, click the file icon, use IDLE GUI

N Each Python module has a built-in __name__ variable that, when it is run as a program and not imported as a library,will be set to the __main__ string by Python.

L command-line arguments

N Example

u Import sys

u Print sys.argv

u If you enter python test.py 1 2 3

u Output [' test.py ', ' 1 ', ' 2 ', ' 3 ']

l sys module

N Example

u Import sys

u print dir (SYS)// display sys contents

u Print len (dir (SYS))// display number of bars

N most of the system interfaces in Python are concentrated in these two modules

u sys

u os

u Other Modules

l glob for file name extension

l socket for network connection and interprocess communication IPC

l Threading, _thread, queue for running and synchronizing concurrent threads

l time, Timeit to get the details about the system's timing

N View Documents

u Import sys

u print (sys.__doc__)

N Sys.path

u a list of directory name strings, each of which represents a running the true search path for the Python interpreter

u when the interpreter starts, the list is based on the PYTHONPATH settings for initialization

N sys.modules

u sys.modules is a dictionary in which each module that your Python session or process imports has a name:module entry

N Other Tools

u sys.argv is displayed as a command-line argument for a list consisting of strings

u sys.stdin sys.stdout sys.stderr Standard Flow

u sys.exit Force exit by invoking

l os module

N Compared to sys is the larger one

N used in operational practice as a portable interface for computer system calls, scripts written with OS and Os.path can often be run on other platforms without modification

N Common Module Tools

u Shell variable os.environ

u Run the program Os.system, Os.popen, OS.EXECV, OS,SPAWNV

u derivation process os.fork, Os.pipe, Os.waitpid, Os,kill

u file descriptor Os.open, Os.read, Os.write

u file processing os.remove, Os.rename, Os.mkfifo, Os.mkdir, Os.rmdir

u Management Tools OS.GETCWD, Os.chdir, Os.chmod, Os.getpid, Os.listdir

u Porting Tools

u Path Name Tool

u Example:

l Import os

l os.getpid ()

L Output 3784

L also open a cmd,#tasklist, find python.exe discovery process pid is 3784

u Example:

l Import os

l os.getcwd ()

L output the current working directory

u Example:

l Import os

l os.system (' dir ')

L Output dir output under normal conditions

u Example:

l Import os

l test = os.popen (' type helloshell.py '). Read ()

L Put the output in test after executing the Shell command

L String Method Base Operation

N Example

u mystr = ' Heheyouhehe '

u Print mystr.find (' you ')// search for specified string

u print mystr.replace (' hehe ', ' haha ')// string substitution

u print ' hehe ' in mystr// Determine if there is a specified string

u Output:

L 4

L Hahayouhaha

L True

N Example

u mystr = ' \ t Ni \ n '

u mystr.strip ()// crop blank separator

u mystr.rstrip ()// crop right blank separator only

u mystr.upper ()// capitalize, but note that mystr itself does not change

u mystr.lower ()// variable lowercase

u mystr.isalpha ()

u mystr.isdigit ()

N Example

u mystr = ' Abcxxdefxxghi '

u delim = ' 88 '

u Print delim.join (mystr.split (' xx '))

u Output Abc88def88ghi

u Note the use of the split method and the Join method

L Basic file Operations

n file = open (' E:\\spam.txt ', ' W ')

N file.write ((' Spam ' * 5) + ' \ n ')

n file.close ()

n file2 = open (' E:\\spam.txt ')

n Text = File.read ()

N Print text

Python system programming (self-Learning Python series notes-3) (not regularly updated)