[Python-Dev] subclassing builtin data structures (original) (raw)
Chris Angelico rosuav at gmail.com
Fri Feb 13 03:40:50 CET 2015
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On Fri, Feb 13, 2015 at 12:46 PM, MRAB <python at mrabarnett.plus.com> wrote:
class BaseInt: ... def init(self, value): ... self.value = value ... def add(self, other): ... return type(self)(self.value + other)
On Fri, Feb 13, 2015 at 11:55 AM, Guido van Rossum <guido at python.org> wrote:
... there is no reason (in general) why the signature of a subclass constructor should match the base class constructor, and it often doesn't.
You're requiring that any subclass of BaseInt be instantiable with one argument, namely its value. That's requiring that the signature of the subclass constructor match the base class constructor.
ChrisA
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