On Wed, Dec 01, 2021 at 09:00:50PM -0800, [email protected] wrote: > Steven D'Aprano > ""If param is missing **or None**, the default if blah..." > The bottom line is: > > you *don't actually* want the parameter to default to the value of a > sentinel.
Yes I do. I *do* want to be able to give a convenient sentinel value in order to explicitly tell the function "give me the default value". > you *have* to use that hack because you can't express what you want the > default to actually be. The point of having default values is so that the caller doesn't have to express what the default will actually be. If the caller has to express that value, it's not a default, it's a passed-in argument. > You're doing something misleading to work around a shortcoming of the > language. How is it misleading? The parameter is explicitly documented as taking None to have a certain effect. None is behaving here as a convenient, common special constant to trigger a certain behaviour, no different than passing (for example) buffering=-1 to open() to trigger a very complex set of behaviour. (With buffering=-1, the buffer depends on the platform details, and whether the file is binary, text, and whether or not it is a tty.) For historical reasons, probably related to C, the default value for buffering is -1. But it could have just as easily be None, or the string "default", or an enumeration, or some builtin constant. -- Steve _______________________________________________ Python-ideas mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/[email protected]/message/QGPPY4JLABDSKICIVJQZ5IRWMXMYAOH4/ Code of Conduct: http://python.org/psf/codeofconduct/
