Python: Respond to Command Line Prompts

Question

I am trying to use Python to interact with another program via the command line. The main problem I am having is a specific call that has multiple follow-up prompts. Initi

Answer 1

Yes, first of all you may create subprocess as an object by:

p = subprocess.Popen('xx viewproject', shell=True, stdin=subprocess.PIPE, 
                      stdout=subprocess.PIPE, universal_newlines=True)

Then you'll have methods like communicate() available, for instance:

newline = os.linesep # [1]
commands = ['y', 'n', 'y', 'n', 'y']
p.communicate( newline.join( commands))

^{1 - os.linesep}

Which will send all the answers at once (and hopefully it'll be enough) relying on the same order of question every time.

You may also try parsing p.stdout and then writing to p.stdin, but this may cause deadlock when one buffer will get full while waiting for another, so be careful with this. Luckily there are some complex examples on google.

Simple version would be:

p = Popen(...)
line = p.stdout.readline() # At this point, if child process will wait for stdin
                           # you have a deadlock on your hands
parse_line( line)
p.stdin.write( newline.join( commands).encode( 'utf-8'))

I would also consider rewriting:

p = subprocess.Popen('si viewproject --project=d:/Projects/test.pj', shell=True, 
                      stdin=subprocess.PIPE, stdout=subprocess.PIPE) 

To:

p = subprocess.Popen( ['si', 'viewproject', '--project=d:/Projects/test.pj'],
                      shell=False, stdin=subprocess.PIPE, stdout=subprocess.PIPE)

Unless you explicitly need Shell invocation.