yhat_sqldf.py 文件源码

def __call__(self, query, env=None):
        """
        Execute the SQL query.
        Automatically creates tables mentioned in the query from dataframes before executing.

        :param query: SQL query string, which can reference pandas dataframes as SQL tables.
        :param env: Variables environment - a dict mapping table names to pandas dataframes.
        If not specified use local and global variables of the caller.
        :return: Pandas dataframe with the result of the SQL query.
        """
        if env is None:
            env = get_outer_frame_variables()

        with self.conn as conn:
            for table_name in extract_table_names(query):
                if table_name not in env:
                    # don't raise error because the table may be already in the database
                    continue
                if self.persist and table_name in self.loaded_tables:
                    # table was loaded before using the same instance, don't do it again
                    continue
                self.loaded_tables.add(table_name)
                write_table(env[table_name], table_name, conn)

            try:
                result = read_sql(query, conn)
            except DatabaseError as ex:
                raise PandaSQLException(ex)
            except ResourceClosedError:
                # query returns nothing
                result = None

        return result