How to wrap "with-usable" object into class?

Question

Suppose we have an object, which is intended to be used with with:

with somefunction() as f:
   ...
   f.somemethod()

Now I want to use it within class, to make object available full lifetime of class instance.

In constructor I would write

class MyClass:
   def __init__(self):
      self.f = somefunction().__enter__()

Where should I call __exit__() then?

You misunderstand the usage of `with`, it's only meant as a convenience, to automatically handle expensive setup and teardown you can't entrust to the user. — cs95, Oct 22 '17 at 13:46
You can add a `__del__` method to your class, but I'd drastically rethink the model instead. — Martijn Pieters, Oct 22 '17 at 13:46
@MartijnPieters yes, I thought about it. What are advantages and disadvantages? — Dims, Oct 22 '17 at 13:56

score 0 · Answer 1 · answered Oct 22 '17 at 13:58

If somefunction is an object, first we could name it someobject and do something like:

class MyClass(object):

    def __init__(self, someobject):
        self._someobject = someobject


    def dothing(self):
        with self._someobject() as so:
            so.somemethod()


myinstance = MyClass(someobject)
myinstance.dothing()

How to wrap "with-usable" object into class?

1 Answers1