Wolfgang Maier <wolfgang.maier <at> biologie.uni-freiburg.de> writes:
>
> Steven D'Aprano <steve+comp.lang.python <at> pearwood.info> writes:
>
> > # With chaining
> > thing = func(MyClass().spam().eggs().cheese(),
> > MyClass().aardvark(),
> > OtherClass().fe().fi().fo().fum(),
> > )
> > do_stuff_with(thing)
> >
> > versus:
> >
> > # Without chaining
> > temp1 = MyClass()
> > temp1.spam()
> > temp1.eggs()
> > temp1.cheese()
> > temp2 = MyClass()
> > temp2.aardvark()
> > temp3 = OtherClass()
> > temp3.fe()
> > temp3.fi()
> > temp3.fo()
> > temp3.fum()
> > thing = func(temp1, temp2, temp3)
> > do_stuff_with(thing)
> >
>
> Another use case might be in comprehensions and generator expressions ??
>
> thing = [MyClass().spam().eggs(x).cheese() for x in sequence]
>
> where you can't use all those temporary assignments.
>
> Best,
> Wolfgang
>
>
Thinking about this, you could define __call__ for your chained class to
return the wrapped object:
class chained:
def __init__(self, obj):
self.obj = obj
def __repr__(self):
return repr(self.obj)
def __getattr__(self, name):
obj = getattr(self.obj, name)
if callable(obj):
def selfie(*args, **kw):
# Call the method just for side-effects, return self.
_ = obj(*args, **kw)
return self
return selfie
else:
return obj
def __call__(self):
return self.obj
This would encourage its localized use on the fly as in:
thing = [MyClass().spam().eggs(x).cheese()() for x in sequence]
where the intention probably would be to generate a list of lists (or other
mutable objects), not of objects of class chained. Localizing the use of
chained also seems like a good idea to me as I do share Peter's worries
about coding style, while I also agree with you that such a class comes in
handy from time to time.
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