Missing bytearray.copy in Python 3

[futursolo]

The superclass MutableSequence of builtin object bytearray is not properly typed in the current stub file(stdlib/3/typing.pyi), which is missing method clear.

[linw1995]

and this,
error: "bytearray" has no attribute "copy"

[ExplodingCabbage]

Looks like this was resolved by #1765

Possible @linw1995's issue is not resolved, though?

Probably makes sense to close this and then open a separate issue for sorting out copy.

[JelleZijlstra]

Making changes to typeshed is easy. Could you just submit a PR adding a copy method to bytearray?

[ExplodingCabbage]

@JelleZijlstra I didn't really understand the rationale for not putting it on MutableSequence given that the docs state that all MutableSequences should have .copy(). I assume this doesn't just affect bytearray, but I'm not sure. I don't feel comfortable that I know what the right resolution is here, but I figure that probably it involves fixing the documentation/implementation inconsistency in collections.abc's MutableSequence, rather than hacking around it on typeshed.

[JelleZijlstra]

There does seem to be a discrepancy between the docs and the implementation, in that the MutableSequence ABC in the stdlib does not define a copy() method. Two solutions:

• Report a bug to CPython about the discrepancy, which would presumably be resolved either by changing the docs or by adding .copy() to the MutableSequence ABC (most likely only in 3.7). Then we could add .copy() to MutableSequence in typeshed, though again probably only for 3.7.
• Add the .copy() method to the stub for bytearray in typeshed. (list, the other prominent MutableSequence, has it already.)

[ExplodingCabbage]

Hmm, I see your rationale. Since even if the issue gets fixed in Python 3.7 we'd want to add .copy() to bytearray anyway to support Python <=3.7, it makes sense to add it now.

Cool, if I get a chance I'll take a look at making that PR - unless somebody else beats me to it.