help needed with subprocess, pipes and parameters

John Pote johnpote at jptechnical.co.uk
Wed Jul 18 00:56:30 CEST 2012


nuffi,

Have you tried running your piped commands

c:\Programs\bob\bob.exe -x -y "C:\text\path\to some\file.txt" | 
c:\Programs\kate\kate.exe -A 2 --dc "Print Media Is Dead" --da "Author" 
--dt "Title" --hf "Times" --bb "14" --aa "" --font "Ariel" - 
"C:\rtf\path\to some\file.rtf"

in a single instance of subprocess? Start it up and use the poll method 
to wait until the subprocess has terminated. Then open the output file 
to get the results.

My recent (and single, hence limited, experience) of using subprocess 
indicated that the spawned process may take a little time to start up. Try

bob = subprocess.Popen([bobPath, '-x', '-y', docpath], stdout = 
subprocess.PIPE,)
time.sleep( 0.5 ) #experiment with the delay
kate = subprocess.Popen([katePath, A, dc, da, dt, hf, fn, bb, path], 
stdin = bob.stdout, stdout = subprocess.PIPE,)

Never looked under the subprocess hood but maybe there's a race 
condition with the kate subprocess starting before the bob subprocess 
has set up its stdout. It's unlikely but so easy to check with a sleep 
between the subprocesses it has to be worth a go.

John


On 13/07/2012 08:34, nuffi wrote:
>
> If I copy and paste the following command into a command window,   it does what I need.
>
> c:\Programs\bob\bob.exe -x -y "C:\text\path\to some\file.txt" | c:\Programs\kate\kate.exe -A 2 --dc "Print Media Is Dead" --da "Author" --dt "Title" --hf "Times" --bb "14" --aa "" --font "Ariel" - "C:\rtf\path\to some\file.rtf"
>
> My mission is to recreate this command within a python script,  so that I can pass a bunch of different parameters into it,  and use it as a batch over a bunch of different papers.
>
> http://docs.python.org/library/subprocess.html seems to be the thing to use in python 2.7.3.  I also checked out http://www.doughellmann.com/PyMOTW/subprocess/.
>
> My attempts run fine,  create destination folders ok and prints done but don't actually seem to process the file.  Is there some way to get subprocess to output the command it's generating so I can see what I'm doing wrong,  rather than just the output of the command?
>
> How can I chekc that kate's opening the pipe left from bob?    Bob may take some time to execute,  will that matter?
>
>
> The code I came up with looks like this:
>
> import os, glob, subprocess
>
> sourceDir = "c:\\text\\"
> destDir = "c:\\rtf\\"
> bobPath = "C:\\Programs\\bob\\bob.exe"
> katePath = "C:\\Programs\\kate\\kate.exe"
>
> def get_new_path(doc):
>      blah = doc.replace(sourceDir, destDir)
>      if not os.path.isdir(blah):
>          os.makedirs(blah)
>      rtf = blah.replace('.txt', '.rtf')
>      pathString = '- "' + (os.path.join(rtf)) + '"'
>      return(pathString)
>
>
> def convert_doc(doc):
>      dc = '--dc "Print Media Is Dead"'
>      da = '--da "Author"'
>      dt = '--dt "Title"'
>      hf = '--hf "Times"'
>      fn = '--font "Ariel"'
>      bb = '--bb "14"'
>      docpath = '"' + (os.path.join(doc)) + '"'
>      path = get_new_path(doc)
>      A = '-A 2'
>      bob = subprocess.Popen([bobPath, '-x', '-y', docpath], stdout = subprocess.PIPE,)
>      kate = subprocess.Popen([katePath, A, dc, da, dt, hf, fn, bb, path], stdin = bob.stdout, stdout = subprocess.PIPE,)
>      end_of_pipe = kate.stdout
>      #print kate
>      #subprocess.call(['echo', "Test peice of text", '>', 'D:\\output.txt'])
>      for line in end_of_pipe:
>          print '\t', blah.strip()
>      #raw_input()
>      return('done')
>
>
> test = convert_doc("c:\\text\\path to\\some\\specific text file.txt")
> print(blah)
>
>
> ==
>
> Thanks for looking  :-)
>



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