Chris Angelico <ros...@gmail.com> writes: > On Tue, Dec 13, 2016 at 10:17 AM, Ben Finney <ben+pyt...@benfinney.id.au> > wrote: > > If the differences didn't matter I would agree that “overly > > pedantic” is fair. But those differences trip up newcomers. Thinking > > of ‘Foo.__init__’ leads people to wonder where the ‘self’ attribute > > came from – am I not meant to be constructing it? — and to attempt > > to return that instance. And when the time comes to lean about > > ‘__new__’ the confusion continues, because the newcomer has been > > told that something *else* is the constructor, so what's this? > > In JavaScript [different semantics apply]. > > Ultimately, every language has slightly different semantics […], so > you have to learn that the "constructor" might have slightly different > semantics.
Please read again the message you extracted that quote from. I already said I'm not claiming some other programming language's semantics should dictate Python's. What I'm saying is that in Python, there *already are* different semantics for a constructor, and they don't match the semantics of ‘Foo.__init__’. In Python, a constructor for a class is a class method. ‘Foo.__new__’ is a constructor. ‘Foo.__init__’ is an instance method, so it's not a constructor. In Python, a constructor for a class makes the instance where it didn't already exist. ‘Foo.__new__’ is a constructor. ‘Foo.__init__’ requires the instance to already be constructed, so it's not a constructor. In Python, a constructor for a class returns a new instance of that class. ‘Foo.__new__’ is a constructor. ‘Foo.__init__’ must return None, so it's not a constructor. In Python, a custom constructor for a class follows the above descriptions. ‘datetime.fromtimestamp’ is a constructor. ‘datetime.__init__’ is not. None of this argues from the semantics of other programming languages, so telling me other languages have different semantics is not a response to this argument. I'm showing that Python classes *already have* constructors, and ‘Foo.__init__’ doesn't qualify because it doesn't have the semantics of Python constructors. -- \ “I've always wanted to be somebody, but I see now that I should | `\ have been more specific.” —Jane Wagner, via Lily Tomlin | _o__) | Ben Finney -- https://mail.python.org/mailman/listinfo/python-list
