py.py 文件源码

def preview_sql(self, url, step, **args):
        """Mocks SQLAlchemy Engine to store all executed calls in a string
        and runs :meth:`PythonScript.run <migrate.versioning.script.py.PythonScript.run>`

        :returns: SQL file
        """
        buf = StringIO()
        args['engine_arg_strategy'] = 'mock'
        args['engine_arg_executor'] = lambda s, p = '': buf.write(str(s) + p)

        @with_engine
        def go(url, step, **kw):
            engine = kw.pop('engine')
            self.run(engine, step)
            return buf.getvalue()

        return go(url, step, **args)