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Should it be possible to subclass TextIO without implementing all abstract methods? #112
Description
Currently this fails:
from typing import TextIO
class MyTextFile(TextIO):
pass
f = MyTextFile() # raises TypeError
The instantiation fails with TypeError: Can't instantiate abstract class MyTextFile with abstract methods <long list of methods>.
Mark Shannon pointed this out. I have to think about whether this is important to support; a simple work-around is to use TextIO.register() instead:
from typing import TextIO
class MyTextFile:
pass
TextIO.register(MyTextFile)
f = MyTextFile() # OK
Activity
NYKevin commentedon May 28, 2015
Some (disjointed) thoughts:
register()?<long list of methods>, why are they included in the abstract class? Could we make some of them mix-in methods instead?<long list of methods>, and we have an instance ofTextIO, should we be prepared to handle anAttributeError?seekable()method which returns True or False) -- could other features provide a similar API?TextReadable,TextWriteable,TextSeekable)?o11c commentedon Oct 20, 2015
Currently, the python2 stubs for
cStringIOare forced to lie because read/write methods are not split into separate base classes. Doubtless there are many other cases, both in python2 and python3.Suggest retitling to
IO[AnyStr].srittau commentedon Nov 4, 2021
I believe this issue is obsolete by now, due to protocols and the suggestion to use protocols for I/O argument types.