spawn or fork

[Eric Brunel]

C Gillespie wrote:
> Dear All,
> 
> I have a function
> def printHello():
>     fp = open('file','w')
>     fp.write('hello')
>     fp.close()
> 
> I would like to call that function using spawn or fork. My questions are:
> 
> 1. Which should I use
> 2. How do I call that function if it is defined in the same file.

spawn execute an external executable program *outside* your current script, 
*not* a Python function. So say you want to run wordpad.exe from your Python 
script, you could do:

os.spawn(os.P_NOWAIT, "C:\\Program files\\Accesories\\wordpad.exe, [...])

So you *need* an external executable to be passed to spawn.

fork works another way: it duplicates the context of your process in another one 
and continues both processes in parallel. So basically, it doesn't *execute* 
anything, but just creates a process. You may then call your function is the new 
process (a.k.a the "child" process):

def printHello():
   ...
if os.fork() == 0:
   ## fork returns 0 in the process copy => this is where we call our function
   printHello()
else:
   ## If fork doesn't return 0, we're in the original => other code
   ...

However, fork is only available on Unices.

What are you trying to do exactly? If you provide more explanations, we may 
provide a better help than the simplistic one above.

HTH
-- 
- Eric Brunel <eric (underscore) brunel (at) despammed (dot) com> -
PragmaDev : Real Time Software Development Tools - http://www.pragmadev.com