你如何相互依赖处理同一模块中的多个Python类？

Question

I'm using an ODM library and I'm defining documents as classes within the same module, when they are related. I've hit a circular dependency problem and because I haven't come across this before in Python, I don't know how to inform the classes of the existence of each other. Example:

''' docs.py '''
from mongoengine import Document
from mongoengine.fields import StringField, ReferenceField, ListField


class Base(Document):
    some_field      = StringField()


class Foo(Base):
    other_field     = StringField()
    another_field   = ReferenceField(Bar)


class Bar(Base):
    other_field     = StringField()
    another_field   = ListField(ReferenceField(Foo))

As it stands the Python will throw a NameError because Bar is not defined when the interpreter gets to a reference to it in the file, within the class Foo . How do I tell Python not to worry and that the class definition will be along shortly?

Answer 1

ReferenceField接受类名。

another_field   = ReferenceField('Bar')