Python concurrent parallel [3]--process--subprocess module

subprocess Module

0 Module Description /Module Description

From subprocess module:

"""Subprocesses with accessible I/O streams this module allows the spawn processes, connect to their Input/output/error p  Ipes, and obtain their return codes.  For a all description of this module see the Python documentation. Main API ======== Run (...): Runs a command, waits for it, and then returns a Completedprocess instance. Popen (...): A class for flexibly executing a command in a new process Constants---------devnull:special value that ind Icates that Os.devnull should is used pipe:special value that indicates a PIPE should be created Stdout:special Valu E that indicates this stderr should go to stdout older API ========= call (...): Runs a command, waits for it to complete , then returns the return code. Check_call (...): Same as Call () but raises calledprocesserror () if return code was not 0 check_output (...): Same as Che Ck_call () but returns the contents of StdOut instead of a return code getoutput (...): Runs a command in the shell, WAIt for it to complete, then returns the output Getstatusoutput (...): Runs a command in the shell, waits for it to COM  Plete, then returns a (status, output) tuple"""  

1 Constants /Constants

1.0 PIPE Constants

constant Value : PIPE =-1

constant Function : A special value that indicates the need to create a pipe. Passing this variable to STDOUT/STDIN/STDERR enables the output of the child process to be passed to the parent process

1.1 STDOUT Constants

constant Value : STDOUT = 2

constant Function : A special value indicating that the stderr needs to be transferred to stdout

1.2 Devnull Constants

constant Value : devnull = 3

constant Function : A special value indicating the need to use the Os.devnull

2 function /Function

2.0 run () function

function Call : Re = Subprocess.run (*popenargs, Input=none, Timeout=none, Check=false)

function function : Create a new process to run the program and return the Completedprocess instance of the new process

Incoming Parameters : *popenargs, input, timeout, check

*popenargs:list type, input used when invoking a new process

Input:obj type, used to set the input of a new process

Timeout:int type, sets the time-out limit and causes timeoutexpired if the process takes too long

Check:bool type, detection program exit, if the exit code is not 0, trigger Calledproecsserror

return Parameters : Re

Re:instance type, returned completedprocess instance

2.1 call () function

function Call : Re = Subprocess.call (*popenargs, Stdin=none, Stdout=none, Stderr=none, shell=false, Timeout=none)

function function : Create new process run program, input output bind to parent process, return new process exit code

Incoming Parameters : *popenargs, stdin, stdout, stderr, Shell, timeout

*popenargs:list type, input used when invoking a new process

Stdin:obj type, used to set the input of a new process

Stdout:obj type, used to set the output of a new process

Stderr:obj type, which sets the error message for the new process

Shell:bool type, set whether to use intermediate shell (can use shell-related variables, etc.)

Timeout:int type, setting time-out limit

return Parameters : Re

Re:int type, return exit code, 0 for normal exit

Note: for the input parameters of the new process, incoming in list form, such as command Python test.py, pass in the parameter list [' Python ', ' test.py '].

2.2 Check_call () function

function call : Re = Subprocess.check_call (*popenargs, Stdin=none, Stdout=none, Stderr=none, Shell=false, Timeout=none)

function function : Create a new process to run the program, the input output bound to the parent process, normal exit return exit code 0, or throw a subprocess. Calledprocesserror

Incoming Parameters : *popenargs, stdin, stdout, stderr, Shell, timeout

*popenargs:list type, input used when invoking a new process

Stdin:obj type, used to set the input of a new process

Stdout:obj type, used to set the output of a new process

Stderr:obj type, which sets the error message for the new process

Shell:bool type, set whether to use intermediate shell (can use shell-related variables, etc.)

Timeout:int type, setting time-out limit

return Parameters : Re

Re:int type, return exit code, 0 for normal exit

2.3 getstatusoutput () function

function Call : Re = subprocess.getstatusoutput (cmd)

function function : Create new process Run program, return new process exit code and output in tuple form

Incoming Parameters : cmd

Cmd:list type, input used when invoking a new process, [' Python ', ' test.py '] form

return Parameters : Re

Re:tuple type, returned tuple, containing exit code and output

2.4 getoutput () function

function Call : Re = subprocess.getoutput (cmd)

function function : Create a new process to run the program, returning the output of the new process as a string

Incoming Parameters : cmd

Cmd:list type, input used when invoking a new process, [' Python ', ' test.py '] form

return Parameters : Re

RE:STR type, return child process output

2.5 check_output () function

function Call : Re = subprocess.check_output (*popenargs, Input=none, Stdin=none,

Stdout=none, Stderr=none, Shell=false, Universal_newlines=false, Timeout=none)

function function : creates a new process to run the program, returning the output of the new process

Incoming Parameters : *popenargs, input, stdin, stdout, stderr, Shell, Universal_newlines, timeout

*popenargs:list type, input used when invoking a new process

INPUT:BYTE/STR type, an additional available input that allows the passing of a word (b) string to stdin

Stdin:obj type, used to set the input of a new process

Stdout:obj type, used to set the output of a new process

Stderr:obj type, which sets the error message for the new process

Shell:bool type, set whether to use intermediate shell (can use shell-related variables, etc.)

Universal_newlines:bool type, set input/output format, false to Byte,true as Str

Timeout:int type, setting time-out limit

return Parameters : Re

RE:BYTE/STR type, returned output result

3 class /Class

3.1 Popen class

class Instantiation: PRCs = subprocess. Popen(args, Stdin=none, Stdout=none, Stderr=none, [...])

functions of the class : used to generate a new process execution subroutine

Incoming Parameters : Args

Args:list type, input for new process execution

Stdin:obj/int type, used to set the input of a new process

Stdout:obj/int type, used to set the output of a new process

Stderr:obj/int type, which sets the error message for the new process

return Parameters : PRCs

Prcs:instance type, generated new process instance

Note: for the input parameters of the new process, args, passed in as list, such as command Python test.py, pass in the parameter list [' Python ', ' test.py '].

3.1.1 PID Properties

Property Call : pid = prcs.pid

Properties Feature : Returns the PID information for a child process

Property Parameters : PID

Pid:int type, PID of child process

3.1.2 Communicate () Method

function Call : Re = prcs.communicate (Input=none, Timeout=none)

function function : used for communication between processes, sending data to stdin, and reading data from stdout and stderr

Incoming Parameters : input, timeout

INPUT:BYTE/STR type, an additional available input that allows the passing of a word (b) string to stdin

Timeout:int type, setting time-out limit

return Parameters : Re

Re:tuple type, returned output, (stdout, stderr)

3.1.3 Poll () Method

function Call : Re = Prcs.poll ()

function function : used to detect whether a child process has ended

Incoming Parameters : No

return Parameters : Re

Re:int type, returns the result that is 1 the child process has ended

3.2 completedprocess class

class Instantiation: Re = Subprocess.run ()/completedprocess (args, ReturnCode, Stdout=none, Stderr=none)

functions of the class : A child process that has finished running, typically returning a build when calling the Subprocess.run () function

Incoming Parameters : args, ReturnCode, stdout, stderr

Args:list type, input for new process execution

Returncode:int type, the child process exit code

Stdout:obj/nonetype type, output of child process, none if not obtained

Stderr:obj/nonetype type, error message for child process, none if not obtained

return Parameters : Re

Re:instance type, generated end child process instance

Python concurrent parallel [3]--process--subprocess module