Python / SQLalchemy - 如何觸發查詢？

Question

我正在努力讓SQLalchemy通過python為我做一些任務。

我可以通過以下示例來實現它，但是我已經停留了一段時間，從for循環移動查詢調用：

for instance in session.query(versions_table).filter(versions_table.c.version==Version):

並通過調用其中一個表結果獲得結果：

 existingID = instance.id

（其中id是返回表的PK）

我不能做的是找到一種隨意觸發查詢的方法，或者作為條件語句的結果，例如

if some conditions met:
 do query
 get / process result

我只能通過調用instance.fieldname來獲取返回的值

任何人都可以指出我哪里出錯了，接受我對SQLalchemy函數的設置/調用方式並不十分滿意。

我想要做的是：

for instance in session.query(versions_table).filter(versions_table.c.version==Version):
 if instance.id == True:  #this is not correct
  print instance.id 
 else:
  print "no match"

更全面的腳本：

from sqlalchemy import *
from sqlalchemy.orm import sessionmaker

engine = create_engine('mysql+mysqldb://u:p@localhost/sqlalchtest',
                   echo=False)

metadata = MetaData(bind=engine)
Session = sessionmaker(bind=engine)
versions_table = Table('versions', metadata, autoload=True)

def doVersionGet(sigfile_filename):
 tree = etree.parse(sigfile_filename)
 root = tree.getroot()
 attributes = root.attrib
 if 'DateCreated' in root.attrib:
  DateCreated = (attributes["DateCreated"])
 if 'Version' in root.attrib:
  Version = (attributes["Version"])
 doVersionPush(DateCreated,Version)

def doVersionPush(DateCreated,Version):
 session = Session() 
 for instance in session.query(versions_table).filter(versions_table.c.version==Version):
  existingID = instance.id 
  #this is not really what I want to do here any way, but this will fire the query every time

if __name__ == "__main__":
 path = "location\sub_sig_files"  ##home_subset for tests
 for (path, dirs, files) in os.walk(path):
  for file in files:
   sigfile_filename = str(path)+"\\"+str(file)
   doVersionGet(sigfile_filename) 

Answer 1

您可以使用Query.all執行查詢， Query.all將執行查詢並返回實例：

instances = session.query(versions_table).filter(versions_table.c.version==Version).all()