On 05/07/2016 03:39 PM, Serhiy Storchaka wrote:
Some types have alternative constructors -- class methods used to create
an instance of the class. For example: int.from_bytes(),
float.fromhex(), dict.fromkeys(), Decimal.from_float().
But what should return these methods for subclasses? Should they return
an instance of base class or an instance of subclass? Almost all
alternative constructors return an instance of subclass (exceptions are
new in 3.6 bytes.fromhex() and bytearray.fromhex() that return bare
bytes and bytearray). But there is a problem, because this allows to
break invariants provided by the main constructor.
Please ignore my comments in that issue. I actually prefer that class
constructors go through the subclass' __new__ and __init__. Overriding
parent class methods for the sole purpose of getting the subclass's type
is quite irritating.
--
~Ethan~
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