使用SQLAlchemy核心: AttributeError：'unicode‘对象没有属性'shares_lineage’

Question

我试图使用SQLAlchemy核心从表中选择数据。

import sqlalchemy as sa
...
with database_engine.connect() as conn:
    s = map(dict, conn.execute(sa.select([destination.c])))
print s

但我得到了以下错误：

/wowcomputers/.virtualenvs/project/lib/python2.7/site-packages/sqlalchemy/sql/selectable.pyc in __init__(self, columns, whereclause, from_obj, distinct, having, correlate, prefixes, suffixes, **kwargs)
   2450             self._raw_columns = []
   2451             for c in columns:
-> 2452                 c = _interpret_as_column_or_from(c)
   2453                 if isinstance(c, ScalarSelect):
   2454                     c = c.self_group(against=operators.comma_op)

/wowcomputers/.virtualenvs/project/lib/python2.7/site-packages/sqlalchemy/sql/elements.pyc in _interpret_as_column_or_from(element)
   3852     # be forgiving as this is an extremely common
   3853     # and known expression
-> 3854     if element == "*":
   3855         guess_is_literal = True
   3856     elif isinstance(element, (numbers.Number)):

<string> in <lambda>(self, other)

/wowcomputers/.virtualenvs/project/lib/python2.7/site-packages/sqlalchemy/sql/base.pyc in __eq__(self, elements, other)
    569         for c in getattr(other, "_all_columns", other):
    570             for local in self._all_columns:
--> 571                 if c.shares_lineage(local):
    572                     l.append(c == local)
    573         return elements.and_(*l)

AttributeError: 'unicode' object has no attribute 'shares_lineage'

我做错了什么？

Answer 1

使用sqlachemy.core执行select时，需要向select传递一个可选选项列表。

sa.select([destination.c.column1, destination.c.column2])

当您只是将所有列传递到select语句时，忘记删除包装列表是一个常见的错误，所以请更改

sa.select([destination.c])

到这个

sa.select(destination.c)