Supporting multiple versions of a Python dependency

Question

I'm the author of an open-source library (N) that provides an enhancement to a popular Python library (P). Recently, P released a new version where they changed some code that affects my library N.

I have a simple fix for N to make it compatible with the new version of P, but I want to know if there's a good way of supporting both versions of P in my library without resorting to an if-else-ing around the different versions. Going forward, I want to support both versions of library P, so just moving to the new one is not an option.

use a virtual environment with the versions that work with your library..same with the new one — Derek Eden
– Derek Eden, Commented Aug 24, 2019 at 0:54
How will virtual environments help me here? I want people to be able to either dynamically install a package depending on their installed P version or failing that, be able to elegantly support multiple versions in my code. — msamogh
– msamogh, Commented Aug 24, 2019 at 8:25
then you'll have to provide both versions and check which dependencies are installed before building your package — Derek Eden
– Derek Eden, Commented Aug 24, 2019 at 15:55

Gabriel Cappelli · Accepted Answer · 2019-09-03 05:09:30Z

1

Many packages have a __version__ attribute.

You can use modules/classes/subclassing to elegantly support multiple versions, but you`ll probably still need one if-else to load the correct implementation.

import marshmallow        
from packaging import version

if version.parse(marshmallow.__version__) >= version.parse("3.0.0"):
    import new_implementation as impl
else:
    import old_implementation as impl

impl.foo()

answered Sep 3, 2019 at 5:09

Gabriel Cappelli

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