Python future.standard_library 模块，suspend_hooks() 实例源码

def test_suspend_hooks(self):
        """
        Code like the try/except block here appears in Pyflakes v0.6.1. This
        method tests whether suspend_hooks() works as advertised.
        """
        example_PY2_check = False
        with standard_library.suspend_hooks():
            # An example of fragile import code that we don't want to break:
            try:
                import builtins
            except ImportError:
                example_PY2_check = True
        if utils.PY2:
            self.assertTrue(example_PY2_check)
        else:
            self.assertFalse(example_PY2_check)
        # The import should succeed again now:
        import builtins

def test_old_urllib_import(self):
        """
        Tests whether an imported module can import the old urllib package.
        Importing future.standard_library in a script should be possible and
        not disrupt any uses of the old Py2 standard library names in modules
        imported by that script.
        """
        code1 = '''
                from future import standard_library
                with standard_library.suspend_hooks():
                    import module_importing_old_urllib
                '''
        self._write_test_script(code1, 'runme.py')
        code2 = '''
                import urllib
                assert 'urlopen' in dir(urllib)
                print('Import succeeded!')
                '''
        self._write_test_script(code2, 'module_importing_old_urllib.py')
        output = self._run_test_script('runme.py')
        print(output)
        self.assertTrue(True)

def test_urllib_imports_install_aliases(self):
        with standard_library.suspend_hooks():
            standard_library.install_aliases()
            import urllib
            import urllib.parse
            import urllib.request
            import urllib.robotparser
            import urllib.error
            import urllib.response
            self.assertTrue(True)