Python `callable` polyfill

Attempts to ensure the callable builtin is available.

On versions of Python where callable is already available, importing this doesn't break anything and leaves callable alone.
On versions without a callable builtin, on import this will attempt to inject an equivalent implementation, so that code invoking callable continues to work.
If your Python runtime has no callable builtin and this module is unable to polyfill it, it will raise a NotImplementedError.

Versioning

This library's version numbers follow the SemVer 2.0.0 specification.

pip install polyfill-callable

Just make sure you run this before you run any other code that uses callable:

import polyfill_callable

You can also catch NotImplementedError if you'd like to gracefully handle the lack of callable:

try:
    import polyfill_callable
except NotImplementedError as error:
    # .. do something ..

Currently, this module only has a callable polyfill for:

The early CPython 3 versions that shipped without callable before it was added back in in CPython 3.2. There we can reimplement it using ctypes, and polyfill it into the global namespace by using builtins.

If there are other Python implementation versions where it would be possible to support a polyfill, they might eventually be added here.