pythonic exec* spawn*

[Nick Craig-Wood]

Daniel Nogradi <nogradi at gmail.com> wrote:
>  Is it possible to pass a python object to a python program as
>  argument?

Yes - you can pickle it.

  http://www.python.org/doc/2.4.2/lib/module-cPickle.html

You can pickle just about anything into a string and unpickle it back
into python objects.  You shouldn't accept pickles from untrusted
sources as this may reperesent a security problem.

>  In my program I would like to start executing an other python program
>  and don't wait until that finishes, only launch it and keep running
>  the original program. The obvious way I can think of it is using the
>  exec* or spawn* function families. However, these are generic
>  functions to start any external program and I was wondering if there
>  was a special way to start a python program (as opposed to an
>  arbitrary program), especially because I would like to pass data to
>  this other program in the form of python objects.
> 
>  While the original program is running it creates all sorts of data in
>  a nice pythonic way, for example as a class instance with lot of
>  member data, and then I wouldn't want to convert all of this into
>  command line arguments because that would create a huge list. I would
>  like to pass the whole object at once to the second python program
>  which should start doing its thing with it while the original program
>  should keep running.
> 
>  I was looking around for threading and forking but couldn't come up
>  with a clear solution.

If you want to fork(), then I would use the subprocess module to
create a child process with a pipe to it.  I would then pass python
objects as pickles back and forth across that pipe.

  http://www.python.org/doc/2.4.2/lib/module-subprocess.html

You'll probably find threading easier though.

  http://www.python.org/doc/2.4.2/lib/module-threading.html

But it will use your multiple CPUs less efficiently than fork()-ing.

-- 
Nick Craig-Wood <nick at craig-wood.com> -- http://www.craig-wood.com/nick