Re: Running External Programs from Within Python

[RayS]

At 10:50 PM 1/31/2004 +0100, Nuff Said wrote:
On Sat, 31 Jan 2004 11:23:42 -0800, Bob=Moore wrote:
If anyone is interested, I used the following non-threaded code; I tried 
pipedream.py, but had apparent timing issues with the threads that I 
couldn't clear up.
I usually use wxPython. An *NIX version would be interesting as well (hint).
The external .exe is an interactive DOS-menu'd program in FORTRAN.

==================  snip  =============================
import os
import time
from wxPython.wx import *
import win32pipe
def getDataFrom(pipe):
    done = False
    timeout = 4 ## seconds
    start_time = time.time()
    data = ''
    error = None
    while not done:
        try:
            ## check to see if the 'file' has any data, using stat()
            #print os.fstat(input.fileno())[6],
            if(os.fstat(pipe.fileno())[6]!=0):
                ## this will read up to a large amount
                data = os.read(pipe.fileno(), 2**16)
            elif(len(data)):
                ## if the read was done on the last loop, we can quit
                done = True
                #print 'read all'
            elif((time.time() - start_time) > timeout):
                ## something went wrong
                done = True
                print 'Error; read timed out'
            else:
                ## might be starting up the remote process...
                time.sleep(.01)
        except (IOError, OSError):
            print '(IOError, OSError)',(IOError, OSError)
            done = True
    return [error, data]
def driveRemote(stdinput, stdoutput, resp):
    """ takes pipes and a string to send
        always gets the current DOS output first... """
    timeOut, result  = getDataFrom(stdoutput)
    if timeOut:
        print 'timedOut resp', result
        return timeOut
    print "remote:'%s'" % result[-60:],
    if (result==('' or None)):
        dlg = wxMessageDialog(parent, "resp not received!"+"\nGot 
'"+result+"'",
          'Error', wxOK | wxICON_INFORMATION)
        try:
            dlg.ShowModal()
        finally:
            dlg.Destroy()
        pgDlg.Destroy()

    ## check for errors
    if (string.find(result, 'run-time error')>-1):
        print resp, '\n'
        dlg = wxMessageDialog(None, result,
          'Error!', wxOK | wxICON_INFORMATION)
        try:
            dlg.ShowModal()
        finally:
            dlg.Destroy()
            return 'error: '+result
    if resp!=None:
        try:
            print resp, '\n'
            os.write(stdinput.fileno(), resp+'\n')
        except IOError, e:
            print 'error; resp, reslt:', resp, result
            print "IOError %s" % e
    return result
## actually start, text mode
stdinput, stdoutput = win32pipe.popen4("FV4R.EXE", 't')
## go through a list of actions
for resp in actionList:
    result = driveRemote(stdinput, stdoutput, resp)
================  snap  =======================
> Can I run (call? exec? eval?) an external program from inside a Python
> program?
>
Check out os.popen (in all it's variants); e.g. something like
the following will do what you want:
  import os
  stdin, stdout, stderr = os.popen3('your program goes here')
  output = stdout.read()
  errors = stderr.read()
  stdin.close(); stdout.close(); stderr.close()
  ... do something with 'output' and 'errors' ...
HTH / Nuff
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