subclassing file objects (to extend open and close operations) in python 3

Question

Suppose I want to extend the built-in file abstraction with extra operations at open and close time. In Python 2.7 this works:

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Answer 1

You could just use a context manager instead. For example this one:

class SpecialFileOpener:
    def __init__ (self, fileName, someOtherParameter):
        self.f = open(fileName)
        # do more stuff
        print(someOtherParameter)
    def __enter__ (self):
        return self.f
    def __exit__ (self, exc_type, exc_value, traceback):
        self.f.close()
        # do more stuff
        print('Everything is over.')

Then you can use it like this:

>>> with SpecialFileOpener('C:\\test.txt', 'Hello world!') as f:
        print(f.read())

Hello world!
foo bar
Everything is over.

Using a context block with with is preferred for file objects (and other resources) anyway.