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只是尝试使用小马 ORM（和 python3.5，sqlite3）进行一些基本练习。我只想打印一些我拥有的数据的选择查询，而不需要进一步处理。Pony orm 似乎根本不喜欢那样......

sqlite 数据库转储

PRAGMA foreign_keys=OFF;
BEGIN TRANSACTION;
CREATE TABLE sums (t text, path BLOB, name BLOB, sum text, primary key (path,name));
INSERT INTO "sums" VALUES('directory','','','');
INSERT INTO "sums" VALUES('file','','sums-backup-f.db','6859b35f9f026317c5df48932f9f2a91');
INSERT INTO "sums" VALUES('file','','md5-tree.py','c7af81d4aad9d00e88db7af950c264c2');
INSERT INTO "sums" VALUES('file','','test.db','a403e9b46e54d6ece851881a895b1953');
INSERT INTO "sums" VALUES('file','','sirius-alexa.db','22a20434cec550a83c675acd849002fa');
INSERT INTO "sums" VALUES('file','','sums-reseau-y.db','1021614f692b5d7bdeef2a45b6b1af5b');
INSERT INTO "sums" VALUES('file','','.md5-tree.py.swp','1c3c195b679e99ef18b3d46044f6e6c5');
INSERT INTO "sums" VALUES('file','','compare-md5.py','cfb4a5b3c7c4e62346aa5e1affef210a');
INSERT INTO "sums" VALUES('file','','charles.local.db','9c50689e8185e5a79fd9077c14636405');
COMMIT;

这是我尝试在 python3.5 交互式 shell 上运行的代码：

from pony.orm import *
db = Database()
class File(db.Entity) :
    _table_ = 'sums'
    t = Required(str)
    path = Required(bytes)
    name = Required(bytes)
    sum = Required(str)
    PrimaryKey(path,name)
db.bind('sqlite','/some/edited/path/test.db')
db.generate_mapping()

File.select().show()

它像这样失败：

Traceback (most recent call last):
  File "/usr/lib/python3.5/site-packages/pony/orm/core.py", line 5149, in _fetch
    try: result = cache.query_results[query_key]
KeyError: (('f', 0, ()), (<pony.orm.ormtypes.SetType object at 0x7fd2d2701708>,), False, None, None, None, False, False, False, ())

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<string>", line 2, in show
  File "/usr/lib/python3.5/site-packages/pony/utils/utils.py", line 75, in cut_traceback
    raise exc  # Set "pony.options.CUT_TRACEBACK = False" to see full traceback
  File "/usr/lib/python3.5/site-packages/pony/utils/utils.py", line 60, in cut_traceback
    try: return func(*args, **kwargs)
  File "/usr/lib/python3.5/site-packages/pony/orm/core.py", line 5256, in show
    query._fetch().show(width)
  File "/usr/lib/python3.5/site-packages/pony/orm/core.py", line 5155, in _fetch
    used_attrs=translator.get_used_attrs())
  File "/usr/lib/python3.5/site-packages/pony/orm/core.py", line 3859, in _fetch_objects
    real_entity_subclass, pkval, avdict = entity._parse_row_(row, attr_offsets)
  File "/usr/lib/python3.5/site-packages/pony/orm/core.py", line 3889, in _parse_row_
    avdict[attr] = attr.parse_value(row, offsets)
  File "/usr/lib/python3.5/site-packages/pony/orm/core.py", line 1922, in parse_value
    val = attr.validate(row[offset], None, attr.entity, from_db=True)
  File "/usr/lib/python3.5/site-packages/pony/orm/core.py", line 2218, in validate
    val = Attribute.validate(attr, val, obj, entity, from_db)
  File "/usr/lib/python3.5/site-packages/pony/orm/core.py", line 1894, in validate
    if from_db: return converter.sql2py(val)
  File "/usr/lib/python3.5/site-packages/pony/orm/dbapiprovider.py", line 619, in sql2py
    if not isinstance(val, buffer): val = buffer(val)
TypeError: string argument without an encoding

我使用这个错误，还是这是一个错误？我不介意提交错误，但这是我第一次使用这个 orm，所以我认为最好先检查一下......

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1 回答 1

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SQLite 有一个（错误）特性，它允许列存储任意值而不管列类型。每个 SQLite 列都具有亲和性，而不是严格的数据类型，而每个值具有在同一列中可以不同的存储类。例如，您可以将文本值存储在整数列中，反之亦然。有关详细信息，请参阅SQLite 第 3 版中的数据类型。

错误的原因是该表在其 BLOB 列中包含“错误”类型的值。正确的 SQLite 二进制文字看起来像x'abcdef'. 您使用的INSERT命令改为插入 UTF8 字符串。

这个问题在最新版本的 Pony中得到了一定程度的修复，您可以从 GitHub 获取。现在，如果 Pony 从 BLOB 列接收到字符串值，它只会保留该值而不抛出异常。

如果您使用 Pony 填充表，它会将 BLOB 数据写入为正确的二进制值，因此以后可以毫无问题地读取它们。

于 2017-04-12T14:10:28.337 回答