Question

I am trying to make a repeated call on the windows command line from my python code. For each fine in a directory, I need to run a command, and wait for it to finish.

try:
    directoryListing = os.listdir(inputDirectory)
    for infile in directoryListing:
        meshlabString = #string to pass to command line
        os.system(meshlabString)

except WindowsError as winErr:
    print("Directory error: " + str((winErr)))

I have been reading online, and it seems the preferred way to do this is with subprocess.call(), but I cannot figure out how to run cmd.exe through subprocess.call(). It kind of works right now using os.system(), but it gets caught up trying to run a bunch of processes at once, and dies. If someone could provide me a few lines of code on how to run a command on the windows command line, and if subprocess.wait() is the best way to wait.

Answer 1

with subprocess, you have a few options. The easiest is call:

import shlex
return_code=subprocess.call(shlex.split(meshlabString))

shlex takes the string and splits it into a list the way the shell would split it. in other words:

shlex.split("this 'is a string' with 5 parts") # ['this', 'is a string', 'with', '5', 'parts]

You could also do:

return_code=subprocess.call(meshlabString,shell=True)

but this way is a security risk if meshlabString is untrusted. Ultimately, subprocess.call is just a wrapper on the subprocess.Popen class, provided for convenience, but it has the functionality that you want here.