未插入Sqlalchemy查询参数

Question

我使用SQLAlchemy declarative来处理MySQL。在

from sqlalchemy import *
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relation, sessionmaker
import datetime

engine = create_engine('mysql+mysqldb://root:mypass@localhost/somedb')

Base = declarative_base()
Base.metadata.bind = engine
DBSession = sessionmaker(bind=engine)
session = DBSession()

class Item(Base):
    __tablename__ = 'item'
    id = Column(Integer, primary_key=True)
    dt = Column(DateTime)
    title = Column(UnicodeText)

Base.metadata.create_all(engine)

i = Item()
i.dt = datetime.datetime.now()
i.title = "hello world"
session.add(i)
session.commit()

此代码对session.commit()引发异常：

^{pr2}$

异常的完整堆栈跟踪在post的末尾。在

我发现参数没有正确地插入到查询字符串中。有一行query = query.format( *db.literal(args) ) in the file MySQLdb/cursors.py, on the line 163。query变量是一个字符串。string.format函数接受替换字段，如{}，{1}，{23}，而不是{}。但是查询变量中的替换字段是%s。在

因此，参数不会插入到查询中。在

我可以通过在sqlalchemy/sql/compiler.py文件中修改变量BIND_TEMPLATES来解决这个问题。我已将'format': "%%s"改为'format': "{}"。在

但是没有炼金术的人明白这一点。问题的真正原因是什么？也许我安装了一些不兼容的版本？在

我在Windows7x64上使用Python3.4， Mysql连接器：Mysql_python-1.2.3-py3.4-win-amd64.egg

异常的完整堆栈跟踪：

Traceback (most recent call last):
  File "C:\Program Files (x86)\JetBrains\PyCharm Community Edition 3.1.3\helpers\pydev\pydevd.py", line 1539, in <module>
    debugger.run(setup['file'], None, None)
  File "C:\Program Files (x86)\JetBrains\PyCharm Community Edition 3.1.3\helpers\pydev\pydevd.py", line 1150, in run
    pydev_imports.execfile(file, globals, locals) #execute the script
  File "C:\Program Files (x86)\JetBrains\PyCharm Community Edition 3.1.3\helpers\pydev\_pydev_execfile.py", line 37, in execfile
    exec(compile(contents+"\n", file, 'exec'), glob, loc) #execute the script
  File "C:/Work/midmay/midmay.parser/scripts/test.py", line 30, in <module>
    session.commit()
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\session.py", line 765, in commit
    self.transaction.commit()
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\session.py", line 370, in commit
    self._prepare_impl()
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\session.py", line 350, in _prepare_impl
    self.session.flush()
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\session.py", line 1903, in flush
    self._flush(objects)
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\session.py", line 2021, in _flush
    transaction.rollback(_capture_exception=True)
  File "C:\Python34\lib\site-packages\sqlalchemy\util\langhelpers.py", line 57, in __exit__
    compat.reraise(exc_type, exc_value, exc_tb)
  File "C:\Python34\lib\site-packages\sqlalchemy\util\compat.py", line 168, in reraise
    raise value
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\session.py", line 1985, in _flush
    flush_context.execute()
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\unitofwork.py", line 370, in execute
    rec.execute(self)
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\unitofwork.py", line 523, in execute
    uow
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\persistence.py", line 64, in save_obj
    mapper, table, insert)
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\persistence.py", line 594, in _emit_insert_statements
    execute(statement, params)
  File "C:\Python34\lib\site-packages\sqlalchemy\engine\base.py", line 720, in execute
    return meth(self, multiparams, params)
  File "C:\Python34\lib\site-packages\sqlalchemy\sql\elements.py", line 317, in _execute_on_connection
    return connection._execute_clauseelement(self, multiparams, params)
  File "C:\Python34\lib\site-packages\sqlalchemy\engine\base.py", line 817, in _execute_clauseelement
    compiled_sql, distilled_params
  File "C:\Python34\lib\site-packages\sqlalchemy\engine\base.py", line 947, in _execute_context
    context)
  File "C:\Python34\lib\site-packages\sqlalchemy\engine\base.py", line 1108, in _handle_dbapi_exception
    exc_info
  File "C:\Python34\lib\site-packages\sqlalchemy\util\compat.py", line 174, in raise_from_cause
    reraise(type(exception), exception, tb=exc_tb, cause=exc_value)
  File "C:\Python34\lib\site-packages\sqlalchemy\util\compat.py", line 167, in reraise
    raise value.with_traceback(tb)
  File "C:\Python34\lib\site-packages\sqlalchemy\engine\base.py", line 940, in _execute_context
    context)
  File "C:\Python34\lib\site-packages\sqlalchemy\engine\default.py", line 435, in do_execute
    cursor.execute(statement, parameters)
  File "C:\Python34\lib\site-packages\mysql_python-1.2.3-py3.4-win-amd64.egg\MySQLdb\cursors.py", line 184, in execute
    self.errorhandler(self, exc, value)
  File "C:\Python34\lib\site-packages\mysql_python-1.2.3-py3.4-win-amd64.egg\MySQLdb\connections.py", line 37, in defaulterrorhandler
    raise errorvalue
  File "C:\Python34\lib\site-packages\mysql_python-1.2.3-py3.4-win-amd64.egg\MySQLdb\cursors.py", line 171, in execute
    r = self._query(query)
  File "C:\Python34\lib\site-packages\mysql_python-1.2.3-py3.4-win-amd64.egg\MySQLdb\cursors.py", line 330, in _query
    rowcount = self._do_query(q)
  File "C:\Python34\lib\site-packages\mysql_python-1.2.3-py3.4-win-amd64.egg\MySQLdb\cursors.py", line 294, in _do_query
    db.query(q)
sqlalchemy.exc.ProgrammingError: (ProgrammingError) (1064, "You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '%s, %s)' at line 1") b'INSERT INTO item (dt, title) VALUES (%s, %s)' (datetime.datetime(2014, 5, 16, 20, 58, 7, 729245), 'hello world')

Answer 1

尝试添加__table_args__ = {}。这对我有用：

from sqlalchemy import *
from sqlalchemy.ext.declarative import declarative_base, DeferredReflection
from sqlalchemy.orm import relation, relationship

DeclarativeBase = declarative_base(cls=DeferredReflection)

class MyItem(DeclarativeBase):
    __tablename__ = 'myitem'
    __table_args__ = {}

更新：我使用python2.7（在Linux上为x64）按原样运行了您的代码（当然除了更改引擎的mysql url字符串之外），它运行起来没有任何问题（它创建了表并在其中插入了“hello world”）。依赖项：

^{pr2}$

仔细阅读您的帖子，我发现您使用的是python3.4。http://docs.sqlalchemy.org/en/rel_0_9/changelog/migration_09.html状态：

“所有SQLAlchemy模块和单元测试现在在2.6以后的任何Python解释器（包括3.1和3.2解释器）中的解释都是一样好的。”

这并没有明确提到3.3和3.4。您可能在SA中遇到了一个bug，或者它还没有更新到3.4版本。我建议安装2.7（它们应该能够在一个系统上共存），使用virtualenvfor2.7，安装deps并重新运行代码。在

MySQL的另一个问题可能是驱动程序。我很遗憾地说，但是在python3.*下对MySQL的支持严重不足：我工作场所的团队发现驱动程序不仅泄漏，而且在高负载下无法处理许多连接。在驱动程序修复之前，你最好使用2.7版本。或者改成Postgres作为数据库。在

Answer 2

我找到了解决办法。也许它不是最好的，也不是所有人都适合。但在这里。 解决方案是安装Mysql连接器，而不是MySQLDb，并将连接字符串从mysql+mysqldb://root:mypass@localhost/somedb更改为mysql+connector://root:mypass@localhost/somedb。在

如果您是Windows用户（和我一样），并且您有以下问题："Cannot open include file: 'config-win.h': No such file or directory" while installing mysql-python，那么您可以将Python版本从3.4降级到3.3，并从这里下载预编译的Mysql Connector for python3.3:http://dev.mysql.com/downloads/connector/python/

它对我有用。谢谢。在