Depending on enum34 from a library

[Ethan Furman]

On 07/24/2016 01:10 PM, Vasiliy Faronov wrote:

> I'm building a Python library where I want to use Python 3.4-style
> enums. Because I need to support Python 2.7, I'm considering using
> enum34 [1]. But I'm not sure how to do this:
>
> If I simply depend on enum34, it will install a module named `enum`
> even in Python 3.4+ environments, and that could shadow the stdlib
> module. Personally I would be very surprised if installing a library
> caused an unrelated stdlib module to be replaced with a third-party
> one, even if it's "just" a backport. However, in my environments,
> `sys.path` is such that stdlib comes before site-packages -- perhaps
> this is normal enough that I can rely on it?
>
> Or I could change my setup.py to include enum34 in `install_requires`
> only if running on Python 2.7. But that will make my distribution's
> metadata dynamic, which doesn't sound like a good idea [2]. At the
> very least, I think it will prevent me from building a universal
> wheel.

enum34 is kept up-to-date, as far as I am able, with the current version of
enum in the stdlib.  As a happy side-effect if it is found before the stdlib
version Python will still run -- at least for Python 3.4 and 3.5; 3.6 is
adding some new features that I am not planning on adding to enum34.

For my own code I use the 'install_requires' option, plus some code that
checks the Python version to see if enum34 is needed.

Your other option is to use aenum [1], my other package, instead; it does
not risk conflict with enum, but has the same basic behavior (plus lots of
advanced behavior you can opt in to).

--
~Ethan~

[1] https://pypi.python.org/pypi/aenum