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: >> None.foo will raise AttributeError. >> > > Right.. As I said, I tried to assume as little as possible about OP's code > and namespace. Didn't want to include C1 in __init__ signature because I > wasn't sure it was available in the namespace. > > It is easy to address, though: > > Example A: > > class C2(object): > def __init__(self, parent=C2): > self.parent = parent
This doesn't work as written (try it!) > Furthermore, having a positional argument will not save us. We can still > break the code if we do the following: > > class C2(object): > def __init__(self, parent): > self.parent = parent > def foo(self): > self.parent.foo() > > c1 = C1() > c2 = C2(None) > c2.foo() > > Making it positional didn't fix our wickedness. The difference is that in this case the fault is on the caller for passing a nonsense value. In the original the fault is on the class author for providing a useless default and implying that the argument is not required. -- https://mail.python.org/mailman/listinfo/python-list
