removeall() in list

[Fredrik Lundh]

castironpi at gmail.com wrote:

> I'm writing an NxN observer pattern, mostly for my own personal
> exploration.  Two threads -might- be calling 'Disconnect' at the same
> time, and I can't even guarantee that the function runs properly.
> 
> 	for emelem in [ e for e in emlist if e.func is func ]:
> 		try:
> 			emlist.remove( emelem )
> 		except ValueError:
> 			pass

so use a lock.  it's a whopping two lines of code:

creation:

     lock = threading.Lock()

usage:

     with lock:
         for emelem in ...
             ...

more here:

     http://effbot.org/zone/thread-synchronization.htm

and btw, looping over a list to figure out what you want to remove from 
that list is a bit pointless.  better just create a new list:

     with lock:
         # get rid of all func instances
         emlist = [e for e in emlist if e.func is not func]

an alternative approach would be to replace emlist with a dictionary, 
keyed on func objects.  that'll let you remove all items associated with 
a given function with a single atomic operation:

     del emdict[func]

</F>