引发ValueError的可选位置参数

Question

我已经构建了一个用于使用CRUD API的database。Retrieve(或Read) function用于表class，assessment_results目前给了我一些问题。关于设计的背景：API还有一个从主文件(object.py)继承来接受string值的方便文件。

它需要做的是:检查一个ID和/或检查两个参数(如果没有使用ID )。如其中一人或另一人(如适当)，则将其连同其详情一并取回。在Python文档之后，我引入了参数*以允许可选的位置参数。我也帮助过这个伟大的教程。 (我是一个设计、构建dbs和使用python的新手)。

我相信检索方法是有效的，但是create_category_rating(...)的设计或方法肯定存在缺陷，因为Traceback正在返回一个ValueError。我在这里读到了堆叠 (类似的问题)，我可能需要为args分配一个值，但我似乎通过了API。

守则如下：

object.py

(检索方法和create_category_rating方法)：

def retrieve_assessment_results(self, something_unique, *args):
    if isinstance(something_unique, int):
        return self.session.query(Assessment_Results).\
        filter(Assessment_Results.id == something_unique).one()
    elif isinstance(something_unique, basestring) and isinstance(args, basestring):
        return self.session.query(Assessment_Results).\
        filter(Assessment_Results.owner == something_unique).\
        filter(Assessment_Results.assessment == args).one()
    elif isinstance(something_unique, Assessment_Results) and isinstance(args, Assessment_Results):
        return something_unique, args
    else:
        raise ValueError('Value being passed is an object')

def create_category_rating(self, category_rating_int, category, assessment_results):
    new_catrating = Category_Rating(category_rating_int, category, assessment_results)
    self.session.add(new_catrating)
    print(new_catrating)
    self.session.commit()
    return(new_catrating)

convenience.py (继承自object.py)

def create_category_rating(self, category_rating_int, category_name, username, name):
    category = self.retrieve_category(category_name)
    owner = self.retrieve_user(username)  
    assessment = self.retrieve_assessment(name)  
    assessment_results = self.retrieve_assessment_results(owner, assessment)
    return super(ConvenienceAPI, self).create_category_rating(category_rating_int, category, assessment_results)

test.py

api = ConvenienceAPI()
api.create_category_rating(2, 'Decision-Making', 'baseball', 'Becoming a Leader')

当前问题：根据建议更改条件(需要解压缩和分配*args提供的元组)。

新API：

def retrieve_assessment_results(self, *args):
    id, assessment, owner = None, None, None
    if len(args) == 1:
        id, = args[0]
    elif len(args) == 2:
        assessment, owner = args
    else:
        raise ValueError('Value being passed is an object')
    if id is not None:
        return self.session.query(Assessment_Results).\
        filter(Assessment_Results.id == id).one()
    elif assessment is not None:
        return self.session.query(Assessment_Results).\
        filter(Assessment_Results.assessment == assessment).one()
    elif owner is not None:
        return self.session.query(Assessment_Results).\
        filter(Assessment_Results.owner == owner).one()

回溯：

Traceback (most recent call last):
  File "/usr/local/lib/python2.7/site-packages/nose/case.py", line 197, in runTest
    self.test(*self.arg)
  File "/Users/ack/code/venv/NotssDB/notssdb/test/test.py", line 111, in test1
    api.create_category_rating(2, 'Decision-Making', 'baseball', 'Becoming a Leader')
  File "/Users/ack/code/venv/NotssDB/notssdb/api/convenience.py", line 41, in create_category_rating
    assessment_results = self.retrieve_assessment_results(owner, assessment)
  File "/Users/ack/code/venv/NotssDB/notssdb/api/object.py", line 323, in retrieve_assessment_results
    filter(Assessment_Results.assessment == assessment).one()
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/orm/query.py", line 2472, in one
    ret = list(self)
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/orm/query.py", line 2515, in __iter__
    return self._execute_and_instances(context)
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/orm/query.py", line 2530, in _execute_and_instances
    result = conn.execute(querycontext.statement, self._params)
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 914, in execute
    return meth(self, multiparams, params)
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/sql/elements.py", line 323, in _execute_on_connection
    return connection._execute_clauseelement(self, multiparams, params)
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 1010, in _execute_clauseelement
    compiled_sql, distilled_params
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 1078, in _execute_context
    None, None)
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 1339, in _handle_dbapi_exception
    exc_info
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/util/compat.py", line 199, in raise_from_cause
    reraise(type(exception), exception, tb=exc_tb)
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 1073, in _execute_context
    context = constructor(dialect, self, conn, *args)
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/engine/default.py", line 544, in _init_compiled
    grp, m in enumerate(parameters)]
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/sql/compiler.py", line 498, in construct_params
    pd[self.bind_names[bindparam]] = bindparam.effective_value
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/sql/elements.py", line 1162, in effective_value
    return self.callable()
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/orm/relationships.py", line 1386, in _go
    value = fn(*arg, **kw)
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/orm/mapper.py", line 2422, in _get_state_attr_by_column
    return state.manager[prop.key].impl.get(state, dict_, passive=passive)
StatementError: (exceptions.KeyError) 'assessment_id' [SQL: u'SELECT assessment_results.id AS assessment_results_id, assessment_results.created_on AS assessment_results_created_on, assessment_results.owner_id AS assessment_results_owner_id, assessment_results.assessment_id AS assessment_results_assessment_id \nFROM assessment_results \nWHERE ? = assessment_results.assessment_id'] [parameters: [immutabledict({})]]

Answer 1

我想我可能发现了这个问题：

elif isinstance(something_unique, basestring) and isinstance(args, basestring):

"args“不是基线:您需要检查每个单独的参数，以确定它是否是基弦。

... and reduce(lambda x, y: x and isinstance(y, basestring), [a for a in args], True)