Python 是否具有等效的 toString()，我可以将 db.Model 元素转换为 String 吗？
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Does Python have a toString() equivalent, and can I convert a db.Model element to String?
提问by Amru E.
I'm writing a ToDo list app to help myself get started with Python. The app is running on GAE and I'm storing todo items in the Data Store. I want to display everyone's items to them, and them alone. The problem is that the app currently displays all items to all users, so I can see what you write, and you see what I write. I thought casting my todo.author object to a string and seeing if it matches the user's name would be a good start, but I can't figure out how to do that.
我正在编写一个待办事项列表应用程序来帮助自己开始使用 Python。该应用程序在 GAE 上运行，我将待办事项存储在数据存储中。我想向他们展示每个人的物品，并且单独展示给他们。问题是该应用程序当前向所有用户显示所有项目，因此我可以看到您写的内容，您也可以看到我写的内容。我认为将我的 todo.author 对象转换为字符串并查看它是否与用户名匹配将是一个好的开始，但我不知道如何做到这一点。
This is what I have in my main.py
这是我在 main.py 中的内容
...
user = users.get_current_user()
if user:
nickname = user.nickname()
todos = Todo.all()
template_values = {'nickname':nickname, 'todos':todos}
...
def post(self):
todo = Todo()
todo.author = users.get_current_user()
todo.item = self.request.get("item")
todo.completed = False
todo.put()
self.redirect('/')
In my index.html I had this originally:
在我的 index.html 中，我最初有这个：
<input type="text" name="item" class="form-prop" placeholder="What needs to be done?" required/>
...
<ul>
{% for todo in todos %}
<input type="checkbox"> {{todo.item}} <hr />
{% endfor %}
</ul>
but I'd like to display items only to the user who created them. I thought of trying
但我只想向创建它们的用户显示项目。我想尝试
{% for todo in todos %}
{% ifequal todo.author nickname %}
<input type="checkbox"> {{todo.item}} <hr />
{% endifequal %}
{% endfor %}
to no avail. The list turns up blank. I assumed it is because todo.author is not a string. Can I read the value out as a string, or can I cast the object to String?
无济于事。列表变成空白。我认为这是因为 todo.author 不是字符串。我可以将值作为字符串读出，还是可以将对象转换为字符串？
Thanks!
谢谢！
Edit: Here is my Todo class
编辑：这是我的 Todo 课程
class Todo(db.Model):
author = db.UserProperty()
item = db.StringProperty()
completed = db.BooleanProperty()
date = db.DateTimeProperty(auto_now_add=True)
Will changing my author to a StringProperty effect anything negatively? Maybe I can forgo casting altogether.
将我的作者更改为 StringProperty 会产生负面影响吗？也许我可以完全放弃铸造。
采纳答案by Jeff Lockhart
In python, the str()methodis similar to the toString()method in other languages. It is called passing the object to convert to a string as a parameter. Internally it calls the __str__()method of the parameter object to get its string representation.
在python中，该str()方法类似于toString()其他语言中的方法。这称为传递对象以转换为字符串作为参数。它在内部调用__str__()参数对象的方法来获取其字符串表示。
In this case, however, you are comparing a UserPropertyauthor from the database, which is of type users.Userwith the nickname string. You will want to compare the nicknameproperty of the author instead with todo.author.nicknamein your template.
但是，在这种情况下，您正在比较UserProperty数据库中的作者，该作者的类型users.User为昵称字符串。您需要将nickname作者的属性与todo.author.nickname模板中的属性进行比较。
回答by Tim Hoffman
str()is the equivalent.
str()是等价的。
However you should be filtering your query. At the moment your query is all()Todo's.
但是，您应该过滤您的查询。目前您的查询是all()Todo 的。
todos = Todo.all().filter('author = ', users.get_current_user().nickname())
or
或者
todos = Todo.all().filter('author = ', users.get_current_user())
depending on what you are defining author as in the Todo model. A StringPropertyor UserProperty.
取决于您在 Todo 模型中定义的作者。AStringProperty或UserProperty。
Note nicknameis a method. You are passing the method and not the result in template values.
注意nickname是一种方法。您正在传递方法而不是模板值中的结果。
回答by Daniel Roseman
You should define the __unicode__method on your model, and the template will call it automatically when you reference the instance.
你应该__unicode__在你的模型上定义方法，当你引用实例时模板会自动调用它。
回答by sinhayash
In function post():
在函数 post() 中：
todo.author = users.get_current_user()
So, to get str(todo.author), you need str(users.get_current_user()). What is returned by get_current_user() function ?
因此，要获得 str(todo.author)，您需要 str(users.get_current_user())。get_current_user() 函数返回什么？
If it is an object, check does it contain a str()" function?
如果它是一个对象，检查它是否包含一个str()" 函数？
I think the error lies there.
我认为错误就在那里。
回答by Amirouche Zeggagh
In Python we can use the __str__()method.
在 Python 中，我们可以使用该__str__()方法。
We can override it in our class like this:
我们可以像这样在我们的类中覆盖它：
class User:
firstName = ''
lastName = ''
...
def __str__(self):
return self.firstName + " " + self.lastName
and when running
和跑步时
print(user)
it will call the function __str__(self)and print the firstName and lastName
它将调用该函数__str__(self)并打印 firstName 和 lastName
