On Monday, 5 March 2018 14:21:54 UTC, Chris Angelico wrote:
> On Tue, Mar 6, 2018 at 12:58 AM, Ooomzay wrote:
> > Here is my fixed example, if someone else could try it in CPython and
> > report back that would be interesting:-
> >
> > class RAIIFileAccess():
> > def __init__(self, fname):
> > print("%s Opened" % fname)
> > self.fname = fname
> >
> > def __del__(self):
> > print("%s Closed" % self.fname)
> >
> > class A():
> > def __init__(self):
> > self.res = RAIIFileAccess("a")
> >
> > class B():
> > def __init__(self):
> > self.res = RAIIFileAccess("b")
> >
> > class C():
> > def __init__(self):
> > self.a = A()
> > self.b = B()
> >
> > def main():
> > c = C()
> > c.dostuff()
> >
> > main()
>
> Here's how I'd do it with context managers.
>
> from contextlib import contextmanager
>
> @contextmanager
> def file_access(fname):
> try:
> print("%s Opened" % fname)
> yield
> finally:
> print("%s Closed" % fname)
>
> @contextmanager
> def c():
> try:
> print("Starting c")
> with file_access("a") as a, file_access("b") as b:
> yield
> finally:
> print("Cleaning up c")
>
> def main():
> with c():
> dostuff() # NameError
Thank you for having a go...
However you have broken the encapsulation of class A and B. These
are trivial for the sake of example. I should have used
_underscores (i.e. self._res) to make the intent of
this example more obvious.
Please try again but preserving the integrity/encapsulation
of class A & B & C, just as the RAII example does.
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