尝试检查对象是否有列表，如果没有则断言

Question

问题：我正在尝试调试 class 中的一个函数，以确保实现了一个列表，如果没有，我希望抛出一个错误。我是编程新手，我试图弄清楚如何有效地添加assert 用于上述调试目的。

在 class BaseAPI() 的方法主体中，我必须遍历列表并为 ConvenienceAPI(BaseAPI) 中的每个项目调用 retrieve_category，将新列表传递给您的 super()。我认为我做错了什么，因为我得到了错误：TypeError: create_assessment() got an unexpected keyword argument 'category'

问题 2 我还希望category 有一个包含多个类别（字符串）的列表。这不是现在发生的。方法中的列表没有被迭代或创建。我不确定...请参阅下面的回溯错误。

代码

实例化categories的列表：

api = BaseAPI()
api.create_assessment('Situation Awareness', 'Developing better skills', 'baseball', 'this is a video','selecting and communicating options', category=['Leadership', 'Decision-Making', 'Situation Awareness', 'Teamwork and Communication'])

assert 和 create 所在的 BaseAPI() 方法

class BaseAPI(object):

    def create_assessment(self, name, text, user, video, element, category):     
        category = [] # Trying to check if category isn't a list
        assert category, 'Category is not a list'
        new_assessment = Assessment(name, text, user, video, element, category)
        self.session.add(new_assessment)
        self.session.commit()

NEW ADD 迭代列表，但仍给出 Error!

class ConvenienceAPI(BaseAPI):          
    def create_assessment(self, name, text, username, videoname, element_text, category_name):
        user = self.retrieve_user(username)
        video = self.retrieve_video(videoname) 
        element = self.retrieve_element(element_text)
        categories = self.retrieve_category(category_name)
            for items in categories: # < ==== added 
            return categories # < ==== added 
        return super(ConvenienceAPI, self).create_assessment(name, text, user, video, element, categories)    

表格

class Assessment(Base):
    __tablename__ = 'assessments'
    #some code

    category_id = Column(Integer, ForeignKey('categories.category_id'))  
    category = relationship('AssessmentCategoryLink', backref='assessments')


    def __init__(self, name, text, user, video, element, category): # OBJECTS !!
        #some code
        self.category = []

TracebackError

ERROR: db.test.test.test1
----------------------------------------------------------------------
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 69, in test1
    api.create_assessment('Situation Awareness', 'Developing better skills', 'baseball', 'this is a video','selecting and communicating options', category=['Leadership', 'Decision-Making', 'Situation Awareness', 'Teamwork and Communication'])
TypeError: create_assessment() got an unexpected keyword argument 'category'

Answer 1

你的断言语句应该是：

assert isinstance(category, list)

同时删除 category = [] 行。

Answer 2

您将类别作为 kwarg 传递，但方法签名期望它作为位置参数。 尝试将方法签名更改为

class BaseAPI(object):
    def create_assessment(self, name, text, user, video, element, category=[]): 

或使用位置参数调用它

return super(ConvenienceAPI, self).create_assessment(
    name, text, user, video, element, category=category
)