def _is_present(self): r""" Run test code to determine whether the shared library is present. EXAMPLES:: sage: from sage.features import CythonFeature sage: empty = CythonFeature("empty", test_code="") sage: empty.is_present() FeatureTestResult('empty', True) """ from sage.misc.temporary_file import tmp_filename with open(tmp_filename(ext=".pyx"), 'w') as pyx: pyx.write(self.test_code) from sage.misc.cython import cython_import try: cython_import(pyx.name, verbose=-1) except CCompilerError: return FeatureTestResult(self, False, reason="Failed to compile test code.") except ImportError: return FeatureTestResult(self, False, reason="Failed to import test code.") except Exception: return FeatureTestResult(self, False, reason="Failed to run test code.") return FeatureTestResult(self, True, reason="Test code compiled and imported.")