On Sun, Mar 2, 2014 at 8:35 PM, Marko Rauhamaa <ma...@pacujo.net> wrote: > However, on the same reference page, os.posix_fadvise() is defined. We > read: > > advice is one of POSIX_FADV_NORMAL, POSIX_FADV_SEQUENTIAL, > POSIX_FADV_RANDOM, POSIX_FADV_NOREUSE, POSIX_FADV_WILLNEED or > POSIX_FADV_DONTNEED > > Now, what kinds of object are those constants? We are not supposed to > know or care. We could peek into the implementation, but it would be a > grave mistake to trust the implementation choices in the application. > > So in my application code I might set: > > favd_flag = os.POSIX_FADV_RANDOM > > in some other part of my code I might want to see how "flag" was set. > Should I use "==" or "is" to test it?
In the absence of any advice to the contrary, I would use == to test. The flags are most likely to be, in order: * An enumeration, in a sufficiently new Python * Integers * Strings * Arbitrary object()s All of the above will compare correctly with ==, and if someone stuffs in an object that compares equal to more than one of them, they're likely to have problems at the far end. If identity is really crucial, I would expect there to be a comment in the docs. And there's another thing you can do to test. >>> import os >>> type(os.POSIX_FADV_RANDOM) <class 'int'> So use ==. If it's later changed and you have to instead use 'is', you can change your code. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
