Opening a Python thread in a new console window

Question

I am trying to make a program that will launch both a view window (console) and a command line. In the view window, it would show constant updates, while the command line window would use raw_input() to accept commands that affect the view window. I am thinking about using threads for this, but I have no idea how to launch a thread in a new console window. How would I do that?

Answer 1

I agree with @stark a GUI is the way.

Purely for illustration here's a not recommended non-GUI way that shows how to do it using a thread, a subprocess, and a named pipe as IPC.

There are two scripts:

• entry.py: accept commands from a user, do something with the command, pass it to the named pipe given at the command-line:

  #!/usr/bin/env python
  import sys
  
  print 'entry console'
  with open(sys.argv[1], 'w') as file:
      for command in iter(lambda: raw_input('>>> '), ''):
          print ''.join(reversed(command)) # do something with it
          print >>file, command # pass the command to view window
          file.flush()
  

• view.py: Launch the entry console, print constant updates in a thread, accept input from the named pipe and pass it to the updates thread:

  #!/usr/bin/env python
  import os
  import subprocess
  import sys
  import tempfile
  from Queue import Queue, Empty
  from threading import Thread
  
  def launch_entry_console(named_pipe):
      if os.name == 'nt': # or use sys.platform for more specific names
          console = ['cmd.exe', '/c'] # or something
      else:
          console = ['xterm', '-e'] # specify your favorite terminal
                                    # emulator here
  
      cmd = ['python', 'entry.py', named_pipe]
      return subprocess.Popen(console + cmd)
  
  def print_updates(queue):
      value = queue.get() # wait until value is available
  
      msg = ""
      while True:
          for c in "/-\|":
              minwidth = len(msg) # make sure previous output is overwritten
              msg = "\r%s %s" % (c, value)
              sys.stdout.write(msg.ljust(minwidth))
              sys.stdout.flush()
  
              try:
                  value = queue.get(timeout=.1) # update value
                  print
              except Empty:
                  pass
  
  print 'view console'
  # launch updates thread
  q = Queue(maxsize=1) # use queue to communicate with the thread
  t = Thread(target=print_updates, args=(q,))
  t.daemon = True # die with the program
  t.start()
  
  # create named pipe to communicate with the entry console
  dirname = tempfile.mkdtemp()
  named_pipe = os.path.join(dirname, 'named_pipe')
  os.mkfifo(named_pipe) #note: there should be an analog on Windows
  try:
      p = launch_entry_console(named_pipe)
      # accept input from the entry console
      with open(named_pipe) as file:
          for line in iter(file.readline, ''):
              # pass it to 'print_updates' thread
              q.put(line.strip()) # block until the value is retrieved
      p.wait()
  finally:
      os.unlink(named_pipe)
      os.rmdir(dirname)
  

To try it, run:

$ python view.py