subclassing "file"

[Uwe Mayer]

Hi,

when extending a build in class, what does the constructor __init__(...)
have to return?
and how does the constructor call its base-class construtor? (or is this
done automatically?)

I want to derive from "file" to create a class that reads record from a
binary file:

class myFile(file):
        def __init__(self, filename, mode="r", bufsize=-1):
                ....?...

just calling the basename and the constructor does not work:

>>> f = myFile("testfile")
>>> f
<closed file '<uninitialized file>', mode '<uninitialized file>' at ...>

What am I missing?

Thanks for your comments
Ciao
Uwe