使用python、sqlalchemy和psycopg2创建PostgreSQL数据库时出错

我使用sqlalchemy，它使用psycopg2连接到postgresql服务器

当我启动以下代码时：

from sqlalchemy.engine.url import URL
from sqlalchemy.engine import create_engine
url = URL(drivername='postgresql', username='myname', password='mypasswd', host='localhost', database='template1')
eng = create_engine(url)
eng.execute('CREATE DATABASE new_db;')

我总是遇到以下错误：

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/engine/base.py", line 1788, in execute
    return connection.execute(statement, *multiparams, **params)
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/engine/base.py", line 1191, in execute
    params)
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/engine/base.py", line 1287, in _execute_text
    return self.__execute_context(context)
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/engine/base.py", line 1302, in __execute_context
    context.parameters[0], context=context)
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/engine/base.py", line 1401, in _cursor_execute
    context)
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/engine/base.py", line 1394, in _cursor_execute
    context)
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/engine/default.py", line 299, in do_execute
    cursor.execute(statement, parameters)
sqlalchemy.exc.InternalError: (InternalError) CREATE DATABASE cannot run inside a transaction block
 'CREATE DATABASE new_db;' {}

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/engine/base.py", line 1787, in execute
    connection = self.contextual_connect(close_with_result=True)
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/engine/base.py", line 1829, in contextual_connect
    self.pool.connect(), 
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/pool.py", line 182, in connect
    return _ConnectionFairy(self).checkout()
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/pool.py", line 369, in __init__
    rec = self._connection_record = pool.get()
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/pool.py", line 213, in get
    return self.do_get()
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/pool.py", line 732, in do_get
    con = self.create_connection()
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/pool.py", line 147, in create_connection
    return _ConnectionRecord(self)
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/pool.py", line 253, in __init__
    self.connection = self.__connect()
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/pool.py", line 319, in __connect
    connection = self.__pool._creator()
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/engine/strategies.py", line 82, in connect
    return dialect.connect(*cargs, **cparams)
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/engine/default.py", line 249, in connect
    return self.dbapi.connect(*cargs, **cparams)
sqlalchemy.exc.OperationalError: (OperationalError) FATAL:  database "roma" does not exist
 None None

我得到以下错误：

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/engine/base.py", line 1788, in execute
    return connection.execute(statement, *multiparams, **params)
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/engine/base.py", line 1191, in execute
    params)
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/engine/base.py", line 1287, in _execute_text
    return self.__execute_context(context)
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/engine/base.py", line 1302, in __execute_context
    context.parameters[0], context=context)
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/engine/base.py", line 1401, in _cursor_execute
    context)
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/engine/base.py", line 1394, in _cursor_execute
    context)
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/engine/default.py", line 299, in do_execute
    cursor.execute(statement, parameters)
sqlalchemy.exc.InternalError: (InternalError) CREATE DATABASE cannot run inside a transaction block
 'CREATE DATABASE new_db;' {}

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/engine/base.py", line 1787, in execute
    connection = self.contextual_connect(close_with_result=True)
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/engine/base.py", line 1829, in contextual_connect
    self.pool.connect(), 
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/pool.py", line 182, in connect
    return _ConnectionFairy(self).checkout()
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/pool.py", line 369, in __init__
    rec = self._connection_record = pool.get()
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/pool.py", line 213, in get
    return self.do_get()
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/pool.py", line 732, in do_get
    con = self.create_connection()
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/pool.py", line 147, in create_connection
    return _ConnectionRecord(self)
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/pool.py", line 253, in __init__
    self.connection = self.__connect()
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/pool.py", line 319, in __connect
    connection = self.__pool._creator()
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/engine/strategies.py", line 82, in connect
    return dialect.connect(*cargs, **cparams)
  File "/usr/local/lib/python2.7/site-packages/SQLAlchemy-0.6.6-py2.7.egg/sqlalchemy/engine/default.py", line 249, in connect
    return self.dbapi.connect(*cargs, **cparams)
sqlalchemy.exc.OperationalError: (OperationalError) FATAL:  database "roma" does not exist
 None None

回溯（最近一次呼叫最后一次）：
文件“”，第1行，在
文件“/usr/local/lib/python2.7/site packages/SQLAlchemy-0.6.6-py2.7.egg/SQLAlchemy/engine/base.py”，执行中的第1787行
连接=self.context\u connect（使用结果=True关闭）
上下文连接中的文件“/usr/local/lib/python2.7/site packages/SQLAlchemy-0.6.6-py2.7.egg/SQLAlchemy/engine/base.py”，第1829行
self.pool.connect（），
文件“/usr/local/lib/python2.7/site packages/SQLAlchemy-0.6.6-py2.7.egg/SQLAlchemy/pool.py”，第182行，在connect中
return _ConnectionFairy（self.checkout（））
文件“/usr/local/lib/python2.7/site packages/SQLAlchemy-0.6.6-py2.7.egg/SQLAlchemy/pool.py”，第369行，在__
rec=self.\u connection\u record=pool.get（）
get中的文件“/usr/local/lib/python2.7/site packages/SQLAlchemy-0.6.6-py2.7.egg/SQLAlchemy/pool.py”，第213行
返回self.do_get（）
文件“/usr/local/lib/python2.7/site packages/SQLAlchemy-0.6.6-py2.7.egg/SQLAlchemy/pool.py”，第732行，在do_get中
con=self.create_connection（）
文件“/usr/local/lib/python2.7/site packages/SQLAlchemy-0.6.6-py2.7.egg/SQLAlchemy/pool.py”，第147行，位于create_connection中
返回连接记录（自身）
文件“/usr/local/lib/python2.7/site packages/SQLAlchemy-0.6.6-py2.7.egg/SQLAlchemy/pool.py”，第253行，在__
self.connection=self.\u connect（）
文件“/usr/local/lib/python2.7/site packages/SQLAlchemy-0.6.6-py2.7.egg/SQLAlchemy/pool.py”，第319行，在u connect中
连接=self.\u池.\u创建者（）
文件“/usr/local/lib/python2.7/site packages/SQLAlchemy-0.6.6-py2.7.egg/SQLAlchemy/engine/strategies.py”，第82行，在connect中
返回方言。连接（*cargs，**cparams）
文件“/usr/local/lib/python2.7/site packages/SQLAlchemy-0.6.6-py2.7.egg/SQLAlchemy/engine/default.py”，第249行，在connect中
返回self.dbapi.connect（*cargs，**cparams）
sqlalchemy.exc.OperationalError:（OperationalError）致命：数据库“roma”不存在
没有

我怎样才能解决这个问题

from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
engine = create_engine('postgresql+psycopg2://USER:PASSWORD@127.0.0.1:5432/DB_OR_TEMPLATE')
session = sessionmaker(bind=engine)()
session.connection().connection.set_isolation_level(0)
session.execute('CREATE DATABASE test')
session.connection().connection.set_isolation_level(1)

如果没有任何数据库，则应使用

template1

"""Isolation level values."""
ISOLATION_LEVEL_AUTOCOMMIT     = 0
ISOLATION_LEVEL_READ_COMMITTED = 1
ISOLATION_LEVEL_SERIALIZABLE   = 2

---

相同，但不使用ORM会话：

conn = eng.connect()
conn.connection.connection.set_isolation_level(0)
conn.execute('create database test')
conn.connection.connection.set_isolation_level(1)

---

当然没有理由使用ORM在普通数据库连接上设置隔离级别，对吗？

POstgresql>11

conn.autocommit=True

谢谢。您的回答确实有帮助。虽然此代码可能会回答此问题，但提供有关此代码为什么和/或如何回答此问题的其他上下文可以提高其长期价值。这并不能回答此问题。若要评论或要求作者澄清，请在其帖子下方留下评论-