On Sun, Mar 25, 2018 at 9:01 AM, Jugurtha Hadjar <jugurtha.had...@gmail.com> wrote: > > On 03/25/2018 03:25 PM, Terry Reedy wrote: >> >> On 3/25/2018 7:42 AM, Jugurtha Hadjar wrote: >> >>> class C2(object): >>> def __init__(self, parent=None): >>> self.parent = parent >> >> >> Since parent is required, it should not be optional. >> > > You can still call it the way you'd call it if it were a positional > argument. > > i.e: > > def foo(keyword_argument=None): > print(keyword_argument) > > foo(3) > foo(keyword_argument=3) > > > Just because it's a keyword argument doesn't mean it's not required. I could > have provided a default using `self.parent = parent or C2`, but I didn't > want to assume C2 was defined in that namespace and wanted to give as > generic a code as I could.
You misunderstand what keyword arguments are. Giving the argument a default does not make it a keyword argument. Passing the argument with keyword syntax is what makes it a keyword argument. It happens at the call site, not when it's defined (with the exception of keyword-only arguments, which this is not). This function takes an argument x either by position or by keyword: def foo(x): pass This function also takes an argument x either by position or by keyword: def foo(x=None): pass The only difference is that the latter makes the argument optional by assigning a default, whereas the former requires it. The point is, if the argument is effectively required and doesn't have a sensible default, then don't make it optional. You can still pass it by keyword if that's what you want. -- https://mail.python.org/mailman/listinfo/python-list
