Build a context manager using yield

- Let's take a deeper look at the inner workings…of a context manager by actually building one.…We can start with the basic framework…that's I've opened up…from 02_02 context manager framework…that includes a context manager decorator,…try, yield and finally statement.…We can turn this into a useful context manager…by putting our setup code in the try block…and our wrap-up code in the finally block.…Here is a simple example from 02_02/incrementer…that will increment the value of an object property…called some property of the object passed in.…

The code here is a function…and because it has a yield statement…rather than a return statement,…our Python interpreter will know…it's a generator function.…And thus, it will return a generator object.…Because it has a context manager decorator,…it will further enhance that object…and it will enable it to act as a context manager…by filling in the enter and exit methods.…The context manager function takes…an object as an argument.…When called, the first thing that will happen…