Synchronization mixin in Python anyone?

[Chris Liechti]

Gustavo Cordova <gcordova at hebmex.com> wrote in 
news:mailman.1020692951.25653.python-list at python.org:
>> Gustavo Cordova <gcordova at hebmex.com> wrote in 
>> news:mailman.1020461587.9261.python-list at python.org:
>>        try:
>>           args = self._args + args
>>           kw.update(self._kw)
>>           return = self._function(*args, **kw)
>>        finally:       
>>           self._lock.release()
>> 
> 
> But what about any exception that's raised?
> 
> Does the finally: clause re-raise the exception so that
> it can be caught upstream?

yes, as Alex already told.
the neat thing about try: finaly: is that it is realy executed in any case, 
no matter what you do in there from "break" over "raise" to "return".

>> the SynchronizedCall wrapper might be too simple for OO. i 
>> think it makes more sense when one method can lock out another
>> on the same instance, like "synchronized" in Java (e.g. get
>> and set methods for an attribute can not be called at the same
>> time). maybe it is that what the OP wanted with his mix-in.
> 
> Yes, I was thinking of something like that with the regex example,
> a way to block between the time a thread enters *any* method of an
> instance, until it exits the method. And that's where it gets
> complicated.
> 
> Maybe with some little hacking of the interpreter, we could make
> a "synchronized" function, like "property()".
> 
> Who knows :-)

i do :)) well after i answered to you post i had to play around with that 
for myself. i've posted a "synchronized" function that you can use like 
"staticmethod". i've posted in a separate message in this thread, but i can 
send it again if you're interested.

it has only a small issue. the first time a synchronized method is called 
is critical - only _one_ thread must do this or more than one lock could be 
created and all but one are lost. but this can easily be solved by making 
__init__ synchronized. this does not harm and is guaranteed to be only 
called once per instace by a single thread.

i don't want that _all_ method get "synchronized" for an instance - just 
selected ones. the reason is that sometimes you need async messages. e.g. 
if that object holds a flag which you want to set but you don't want to 
wait because an other thread uses a method.

chris

-- 
Chris <cliechti at gmx.net>