Easily write backwards-and-forwards compatible libraries.


If you have a library, you may want it to run across multiple python release versions. You might want to prefer certain features that aren’t available in older versions. Use compatlib to keep your code clean.


import asyncio
from compatlib import compat

@compat.after(3, 4)
def main() -> None:
    return 3.4

@compat.after(3, 7)
def main() -> None:
    return 3.7

compatlib will resolve the latest-usable version at runtime, by comparing the overloaded methods with the interpreter sys.version_info.

When running the above code on python 3.6, it will use the first main. If you run it on python 3.7 it will run the second main.


Thanks to @wesselb for authoring the great plum multiple dispatch library, which compatlib uses as the basis of its decorator implementation. Instead of dispatching on type signatures, it dispatches on sys.version_info tuples.


  • Support dispatching on versions of libraries.
  • Support dispatching on the presence of an attribute (effectively, a boolean dispatcher)


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