__init__.py 文件源码

def _available_backends():
    global _available_backends_list

    if _available_backends_list is None:
        entry_point_backends = [
            # DeprecatedIn16
            # setuptools 11.3 deprecated support for the require parameter to
            # load(), and introduced the new resolve() method instead.
            # We previously removed this fallback, but users are having issues
            # where Python loads an older setuptools due to various syspath
            # weirdness.
            ep.resolve() if hasattr(ep, "resolve") else ep.load(require=False)
            for ep in pkg_resources.iter_entry_points(
                "cryptography.backends"
            )
        ]

        _available_backends_list = _backend_import_fallback(
            entry_point_backends
        )

    return _available_backends_list