How do you deal with circular imports ?

For example I have models like this :

# modules/patients/models.py
class Patient(db.Model, OwnerMixin):	
	__owner_backref_name__ = "patients"

	id = db.Column(db.Integer, primary_key=True)

	phone = db.Column(db.String)
	email = db.Column(db.String)
	first_name = db.Column(db.String)
	last_name = db.Column(db.String)
	birthday = db.Column(db.DateTime)
	zip_code = db.Column(db.String)
	address = db.Column(db.String)

        # I would like to do this, but there's circular import....
       @aggregated('claims', db.Column(db.Integer))
	def unpaid_amount(self):
		return db.func.count('1')

# modules/accounting/models.py
class Claim(db.Model, OwnerMixin):
	__owner_backref_name__ = 'claims'

	id = db.Column(db.Integer, primary_key=True)

	date = db.Column(db.DateTime, nullable=False)
	label = db.Column(db.String, nullable=False)
	amount = db.Column(db.Float, nullable=False)
	ref = db.Column(db.String)	

	patient_id = db.Column(db.Integer, db.ForeignKey('patient.id'), nullable=False)
	patient = db.relationship(
				Patient,
				backref=db.backref('claims', cascade="delete, delete-orphan")
	)

Patient is in dedicated module “patient” and claim model is in ‘accounting’ modules with other models related to accounting. The problem is I can’t import claim model and I can’t access to claim model in patient model in order to, for example, make the sum of claims amount. I think this is some design issue, but I want to be sure if there’s any workaround before rewriting…

[askz]

Yes this is what I’ve been up these last minutes. Many thanks. I resolved it with this solution plus :

	@aggregated('claims', db.Column(db.Integer))
	def unpaid_sum(self):
		return db.func.sum(Claim.amount)

[khorolets]

@askz And what about @frol’s advice about providing related model as string without importing it? Didn’t it help?

patient = db.relationship(
    'Patient',
    backref=db.backref('claims', cascade="delete, delete-orphan")
)

@frol should it work?