version.py 文件源码

def _get_version_from_pkg_resources(self):
        """Obtain a version from pkg_resources or setup-time logic if missing.

        This will try to get the version of the package from the pkg_resources
        record associated with the package, and if there is no such record
        falls back to the logic sdist would use.
        """
        # Lazy import because pkg_resources is costly to import so defer until
        # we absolutely need it.
        import pkg_resources
        try:
            requirement = pkg_resources.Requirement.parse(self.package)
            provider = pkg_resources.get_provider(requirement)
            result_string = provider.version
        except pkg_resources.DistributionNotFound:
            # The most likely cause for this is running tests in a tree
            # produced from a tarball where the package itself has not been
            # installed into anything. Revert to setup-time logic.
            from pbr import packaging
            result_string = packaging.get_version(self.package)
        return SemanticVersion.from_pip_string(result_string)