【Python】 Subprocess module

1. subprocess.check_output()

2.subprocess.call()

3. subprocess.check_call()

the methods 1.2.3 are are wrapper of subprocess.Popen()

• example 1:

Open Visual Studio through python

This way is incorrect.

>>> retcode = subprocess.call('devenv.exe', shell=True)
'devenv.exe' is not recognized as an internal or external command,
operable program or batch file.

Another way:

retcode = subprocess.call("C:\Program Files (x86)\Microsoft Visual Studio 12.0\Common7\IDE\devenv.exe",shell=True)

　　It's done.

Your VS is opened. But the invoke process is blocked. You have to close the process you spawned to get the return code.

• example 2:

try to run iisreset command with python

>>> print subprocess.check_call("iisreset", shell = True)
 
Attempting stop...
Internet services successfully stopped
Attempting start...
Internet services successfully restarted
0

class Popen(args, bufsize=0, executable=None, stdin=None, stdout=None, stderr=None, preexec_fn=None, close_fds=False, shell=False, cwd=None, env=None, universal_newlines=False, startupinfo=None, creationflags=0)

What the Popen returns is a child process you want to create.

example 3:

the Popen() process will not be blocked unless we explicit child.wait()

import subprocess
def havewait():
    child = subprocess.Popen(['ping','vwijin014'])
    child.wait()
    print 'parent process'
 
def nowait():
    child = subprocess.Popen(['ping','vwijin014'])
    #child.wait()
    print 'parent process'

Pay attention to the red line order. One is before the ping running.