Partial Function Application and implicit self problem

[Gabriel Rossetti]

Hello,

I am using Partial Function Application in a class and I've come up with
a problem, when the method is called it tries to pass "self" to the
curried/partial function, but this should be the first argument in
reality, but since the function is curried, then the self gets passed as
the second argument. Here is the code :

def __registerService(self, atomic, service):
def reg(service):
# registers the service
...

if(atomic):
# Lock the service dict and register the service, then unlock it
self.__mutex.lock(reg, service)
self.__mutex.unlock()
else:
reg(service)

registerServiceAtomic = partial(__registerService, True)
registerServiceNonAtomic = partial(__registerService, False)

I should pass self when applying partial, but then I can't do that since
self is not available there. Does anyone have any ideas?

Thanks,
Gabriel

 

[Diez B. Roggisch]

Hello,

I am using Partial Function Application in a class and I've come up with
a problem, when the method is called it tries to pass "self" to the
curried/partial function, but this should be the first argument in
reality, but since the function is curried, then the self gets passed as
the second argument. Here is the code :

def __registerService(self, atomic, service):
def reg(service):
# registers the service
...
if(atomic):
# Lock the service dict and register the service, then unlock it
self.__mutex.lock(reg, service)
self.__mutex.unlock()
else:
reg(service)
registerServiceAtomic = partial(__registerService, True)
registerServiceNonAtomic = partial(__registerService, False)

I should pass self when applying partial, but then I can't do that since
self is not available there. Does anyone have any ideas?

Use a bound-method instead. That has the self already bound to it. Like
this:


class Foo:
def m(self, arg):
print arg

f = Foo()
partial(f.m, 10)


Diez

 

[Gabriel Rossetti]

Use a bound-method instead. That has the self already bound to it. Like
this:


class Foo:
def m(self, arg):
print arg

f = Foo()
partial(f.m, 10)


Diez

Ok, thanks, I moved the partial defs to __init__() and now it seams to
work (I still have a but elsewhere, but this part no longer gives an error :


def __init__():
self.registerServiceAtomic = partial(self.__registerService, True)
self.registerServiceNonAtomic = partial(self.__registerService, False)

def __registerService(self, atomic, service):
def reg(service):
# registers the service
...

if(atomic):
# Lock the service dict and register the service, then unlock it
self.__mutex.lock(reg, service)
self.__mutex.unlock()
else:
reg(service)


Thanks,
Gabriel

 

[Gabriel Genellina]

En Thu, 27 Mar 2008 05:40:30 -0300, Gabriel Rossetti

I see that you've already solved your original problem. But looking at
those names, I wonder if you're using the mutex module; note that such
"mutex" is absolutely useless in a multithreaded program, it doesn't
guarantee mutual exclusion, the "atomic" testandset operation isn't atomic
at all, by example.
For a "real" mutex, use a threading.Lock object.

 

[Gabriel Rossetti]

Gabriel Rossetti a écrit :

registerServiceAtomic = partial(__registerService, atomic=True)
registerServiceNonAtomic = partial(__registerService, atomic=False)

Caveat: you'll have to either invert the order of the atomic and
service params, or call the partials with named arg for service.

HTH

Ok, thanks, I didn't know you could do that, I though partial was always
left to right (I had read that about curry)

Gabriel

 

[Bruno Desthuilliers]

Gabriel Rossetti a écrit :

Ok, thanks, I didn't know you could do that, I though partial was always
left to right

It's left to right for positional arguments. Using named arguments, you
can pass them in whatever order.

(I had read that about curry)

Which 'curry' ?-)

 

[castironpi]

Gabriel Rossetti a écrit :







It's left to right for positional arguments. Using named arguments, you
can pass them in whatever order.


Which 'curry' ?-)

I think 'prefix' should go in there. Can you try: partial( G.f, a, b )
( self= obj )? (If that's too brief let me know.)