ndb.StringProperty如何等于一个python字符串? [英] How is ndb.StringProperty equals a python string?
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问题描述
我有这个ndb模型类
class foo(ndb.Model):
abc = ndb.StringProperty ()
现在当我使用 abc
这:
if foo.abc ==a:
print我在!
它进入if块并打印我进来了!
这可能怎么样?
我也试过打印 foo .abc
,它返回 StringProperty('abc')
解决方案<
class Foo(ndb.Model) :
abc = ndb.StringProperty()
foo = Foo()
foo.abc ='some val'
print foo.abc#prints'some val '
print foo.abc =='a'#打印False
print Foo.abc =='a'#打印一些不是布尔值的 - 现在不能检查。
您正在获取我在!
,因为ndb属性覆盖 __等于__
运算符并返回一个被视为 True
的非空对象。这用于使查询像 query.filter(foo.abc =='def')
I have this ndb Model class
class foo(ndb.Model):
abc = ndb.StringProperty()
Now when I used abc
like this:
if foo.abc == "a":
print "I'm in!"
It gets into the if block and prints I'm in!
How's this possible?
I also tried printing foo.abc
, it returned StringProperty('abc')
解决方案
You have to instantiate an instance of class to use properties properly.
class Foo(ndb.Model):
abc = ndb.StringProperty()
foo = Foo()
foo.abc = 'some val'
print foo.abc # prints 'some val'
print foo.abc == 'a' # prints False
print Foo.abc == 'a' # prints something not boolean - can't check now.
You are are getting "I'm in!"
because ndb properties are overwriting __equal__
operator and returning a non empty object that is treated as True
. This is used to make queries like query.filter(foo.abc == 'def')
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