dataframe写入postgresql数据库中

 import cStringIO

 output = cStringIO.StringIO()
 # ignore the index
 df_a.to_csv(output, sep='\t',index = False, header = False)
 output.getvalue()
 # jump to start of stream
 output.seek(0)

 connection = engine.raw_connection() #engine 是 from sqlalchemy import create_engine
 cursor = connection.cursor()
 # null value become ''
 cursor.copy_from(output,table_name,null='')
 connection.commit()
 cursor.close()