Asynchronous function calling with python and GTK.

async.py

import threading
from gi.repository import GObject

# calls f on another thread
def async_call(f, on_done):
  """
  Starts a new thread that calls f and schedules on_done to be run (on the main
  thread) when GTK is not busy.

  Args:
    f (function): the function to call asynchronously. No arguments are passed
                  to it. f should not use any resources used by the main thread,
                  at least not without locking.

    on_done (function): the function that is called when f completes. It is
                        passed f's result as the first argument and whatever
                        was thrown (if anything) as the second. on_done is
                        called on the main thread, so it can access resources
                        on the main thread.

  Returns:
    Nothing.

  Raises:
    Nothing.
  """

  if not on_done:
    on_done = lambda r, e: None

  def do_call():
    result = None
    error = None

    try:
      result = f()
    except Exception, err:
      error = err

    GObject.idle_add(lambda: on_done(result, error))

  thread = threading.Thread(target = do_call)
  thread.start()

# free function decorator
def async_function(on_done = None):
  """
  A decorator that can be used on free functions so they will always be called
  asynchronously. The decorated function should not use any resources shared
  by the main thread.

  Example:
  @async_function(on_done = do_whatever_done)
  def do_whatever(look, at, all, the, pretty, args):
    # ...

  Args:
    on_done (function): the function that is called when the decorated function
                        completes. If omitted or set to None this will default
                        to a no-op. This function will be called on the main
                        thread.

                        on_done is called with the decorated function's result
                        and any raised exception.

  Returns:
    A wrapper function that calls the decorated function on a new thread.

  Raises:
    Nothing.
  """

  def wrapper(f):
    def run(*args, **kwargs):
      async_call(lambda: f(*args, **kwargs), on_done)
    return run
  return wrapper

# method decorator
def async_method(on_done = None):
  """
  A decorator that can be used on class methods so they will always be called
  asynchronously. The decorated function should not use any resources shared
  by the main thread.

  Example:
  @async_method(on_done = lambda self, result, error: self.on_whatever_done(result, error))
  def do_whatever(self, look, at, all, the, pretty, args):
    # ...

  Args:
    on_done (function): the function that is called when the decorated function
                        completes. If omitted or set to None this will default
                        to a no-op. This function will be called on the main
                        thread.

                        on_done is called with the class instance used, the
                        decorated function's result and any raised exception.

  Returns:
    A wrapper function that calls the decorated function on a new thread.

  Raises:
    Nothing.
  """

  if not on_done:
    on_done = lambda s, r, e: None

  def wrapper(f):
    def run(self, *args, **kwargs):
      async_call(lambda: f(self, *args, **kwargs), lambda r, e: on_done(self, r, e))
    return run
  return wrapper