错误：尝试通过 sqlalchemy 在 postgresql 中创建数据库时出现 psycopg2.OperationalError [关闭]答案

【问题标题】：error: psycopg2.OperationalError when trying to create a database in postgresql via sqlalchemy [closed]错误：尝试通过 sqlalchemy 在 postgresql 中创建数据库时出现 psycopg2.OperationalError [关闭]
【发布时间】：2020-02-25 01:50:30
【问题描述】：

我正在尝试通过 sqlalchemy 在 postgresql 中创建一个数据库。当我尝试运行以下代码时：

import sqlalchemy
from sqlalchemy import create_engine
from sqlalchemy import Column, Integer, String, ForeignKey, MetaData
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm.session import sessionmaker
import psycopg2

engine = create_engine('postgresql://scott:tiger@localhost/postgres')
#connection = engine.connect()
base = declarative_base()

class schedule(base):
    __tablename__ = 'schedule'
    id = Column(Integer, primary_key=True)
    time = Column(String)
    monday = Column(String)
    tuesday = Column(String)
    wednesday = Column(String)
    thursday = Column(String)
    friday = Column(String)
    saturday = Column(String)

base.metadata.create_all(engine)

我收到一个错误：psycopg2.OperationalError

错误追溯：

Traceback (most recent call last):
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\engine\base.py", line 2275, in _wrap_pool_connect
    return fn()
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\pool\base.py", line 363, in connect
    return _ConnectionFairy._checkout(self)
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\pool\base.py", line 760, in _checkout
    fairy = _ConnectionRecord.checkout(pool)
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\pool\base.py", line 492, in checkout
    rec = pool._do_get()
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\pool\impl.py", line 139, in _do_get
    self._dec_overflow()
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\util\langhelpers.py", line 68, in __exit__
    compat.reraise(exc_type, exc_value, exc_tb)
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\util\compat.py", line 153, in reraise
    raise value
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\pool\impl.py", line 136, in _do_get
    return self._create_connection()
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\pool\base.py", line 308, in _create_connection
    return _ConnectionRecord(self)
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\pool\base.py", line 437, in __init__
    self.__connect(first_connect_check=True)
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\pool\base.py", line 639, in __connect
    connection = pool._invoke_creator(self)
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\engine\strategies.py", line 114, in connect
    return dialect.connect(*cargs, **cparams)
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\engine\default.py", line 481, in connect
    return self.dbapi.connect(*cargs, **cparams)
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\psycopg2\__init__.py", line 126, in connect
    conn = _connect(dsn, connection_factory=connection_factory, **kwasync)
psycopg2.OperationalError

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "c:\program files (x86)\microsoft visual studio\2019\enterprise\common7\ide\extensions\microsoft\python\core\ptvsd_launcher.py", line 119, in <module>
    vspd.debug(filename, port_num, debug_id, debug_options, run_as)
  File "c:\program files (x86)\microsoft visual studio\2019\enterprise\common7\ide\extensions\microsoft\python\core\Packages\ptvsd\debugger.py", line 39, in debug
    run()
  File "c:\program files (x86)\microsoft visual studio\2019\enterprise\common7\ide\extensions\microsoft\python\core\Packages\ptvsd\__main__.py", line 316, in run_file
    runpy.run_path(target, run_name='__main__')
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\runpy.py", line 263, in run_path
    pkg_name=pkg_name, script_name=fname)
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\runpy.py", line 96, in _run_module_code
    mod_name, mod_spec, pkg_name, script_name)
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "H:\prog_vs\chatBot\chatBot\chatBot\chatBot.py", line 23, in <module>
    base.metadata.create_all(engine)
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\sql\schema.py", line 4304, in create_all
    ddl.SchemaGenerator, self, checkfirst=checkfirst, tables=tables
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\engine\base.py", line 2045, in _run_visitor
    with self._optional_conn_ctx_manager(connection) as conn:
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\contextlib.py", line 112, in __enter__
    return next(self.gen)
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\engine\base.py", line 2037, in _optional_conn_ctx_manager
    with self._contextual_connect() as conn:
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\engine\base.py", line 2239, in _contextual_connect
    self._wrap_pool_connect(self.pool.connect, None),
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\engine\base.py", line 2279, in _wrap_pool_connect
    e, dialect, self
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\engine\base.py", line 1544, in _handle_dbapi_exception_noconnection
    util.raise_from_cause(sqlalchemy_exception, exc_info)
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\util\compat.py", line 398, in raise_from_cause
    reraise(type(exception), exception, tb=exc_tb, cause=cause)
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\util\compat.py", line 152, in reraise
    raise value.with_traceback(tb)
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\engine\base.py", line 2275, in _wrap_pool_connect
    return fn()
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\pool\base.py", line 363, in connect
    return _ConnectionFairy._checkout(self)
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\pool\base.py", line 760, in _checkout
    fairy = _ConnectionRecord.checkout(pool)
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\pool\base.py", line 492, in checkout
    rec = pool._do_get()
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\pool\impl.py", line 139, in _do_get
    self._dec_overflow()
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\util\langhelpers.py", line 68, in __exit__
    compat.reraise(exc_type, exc_value, exc_tb)
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\util\compat.py", line 153, in reraise
    raise value
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\pool\impl.py", line 136, in _do_get
    return self._create_connection()
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\pool\base.py", line 308, in _create_connection
    return _ConnectionRecord(self)
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\pool\base.py", line 437, in __init__
    self.__connect(first_connect_check=True)
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\pool\base.py", line 639, in __connect
    connection = pool._invoke_creator(self)
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\engine\strategies.py", line 114, in connect
    return dialect.connect(*cargs, **cparams)
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\sqlalchemy\engine\default.py", line 481, in connect
    return self.dbapi.connect(*cargs, **cparams)
  File "C:\Users\Nikola\AppData\Local\Programs\Python\Python37\lib\site-packages\psycopg2\__init__.py", line 126, in connect
    conn = _connect(dsn, connection_factory=connection_factory, **kwasync)
sqlalchemy.exc.OperationalError: (psycopg2.OperationalError)
(Background on this error at: http://sqlalche.me/e/e3q8)
Press any key to continue . . .

数据库是这样的

enter image description here

【问题讨论】：

连接字符串'postgresql://scott:tiger@localhost/postgres'是实际的连接字符串，还是这个问题的占位符？看起来这归结为无法连接。
这是我实际使用的。我取自：docs.sqlalchemy.org/en/13/core/engines.html 段落：PostgreSQL 如果更准确地说是行：engine = create_engine('postgresql://scott:tiger@localhost/mydatabase') 我只将“mydatabase”更改为实际的。
在这种情况下，您的数据库很可能没有密码为“tiger”的用户“scott”。
非常感谢您清晰而礼貌的回答（我知道这个问题很愚蠢）。错误正是你所说的。除此之外，我半天不明白数据库还有一个用户。我之前曾尝试使用 Windows 帐户用户。
这些是 cmets，还不是正确的答案。如果写了答案，请按照以下说明操作：stackoverflow.com/help/someone-answers。我不完全确定，但我认为您也应该能够自己回答——而且这样做是完全可以接受的——除非我忘记了一些适用的声誉限制。

标签： python postgresql sqlalchemy psycopg2

【解决方案1】：

@ilja-everilä 的评论回答了这个问题：

连接字符串 'postgresql://scott:tiger@localhost/postgres' 是实际的连接字符串，还是这个问题的占位符？看起来这归结为无法连接。

数据库连接 URI 仍在使用对数据库无效的占位符凭据（用户“scott”，密码“tiger”）。

【讨论】：