CODEWITHSUNDEEP
pythonpython-3.xpython-2.7
Kaitain
Kaitain

Reputation: 960

Is there a clean way to add Python 3-only functionality to a class whose other functionality is used in 2.7?

I'm creating a project in Python that I intend to be able to run under both Python 2.7 and Python 3. I created a class where it became apparent that a nice piece of functionality was available under Python 3 using some Python 3-specific functionality. I don't believe I can replicate the same functionality in Python 2.7, and am not trying to do so. But I intend for the Python 3 app to perhaps have some additional functionality as a consequence.

Anyway, I was hoping that so long as the 2.7 app never called the functions that used the 3.x functionality I'd be okay. But, no, because the presence of the code generates a compile-time error in 2.7, so it spits the dummy despite the function never being called at runtime. And because of Python's lack of any compile-time guards I'm not entirely sure what the best solution is.

I guess I could create a subclass of MyClass, call it MyClass3, put it in another module and add the extra functions there. But that makes a lot of things substantially grubbier...many more split code paths based on sys.version_info, circular inclusion problems unless I do a lot of file-splitting and...(waves hand). It's a mess that way. But maybe it's the only option available?

EDIT: The original question made reference to "yield from" which is why the answer below discusses it. But the original question was not actually looking for advice on how to get "yield from" working in 2.7, but the moderator seemed to THINK this was what the question was about and flagged it as a duplicate accordingly.

As it happened, just as I edited the question to focus it on the issue of organizing the project to avoid compile errors (and to remove references to "yield from"), an answer came in that referenced the yield from issue and turned out to be super-useful.

Upvotes: 2

Views: 61

Answers (1)

sophros
sophros

Reputation: 16660

yield from was backported to Python 2.7 in the following module: yieldfrom.

There is also a SO question about implementing yield from functionality back to python 2 that you may find useful as well as a blog post on the same topic.

AFAIK, there is no official backport of the functionality so there is nothing like from __future__ import yieldfrom that one could expect (please correct if you know otherwise).

Upvotes: 1

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