Cannot update table via sqlalchemy

问题

I'm trying to update a row after a select

instance = session.query(Scouts).filter(Scouts.camp == camp, Scouts.user == user,Scouts.gender == gender).first()
instance.number_of_visits += 1
session.commit()

My Scouts class looks like:

class Scouts(Base):
    __tablename__ = 'scouts'
    camp = Column(String, primary_key=True)
    user = Column(Integer)
    gender = Column(String)
    number_of_visits = Column(Integer)

    def __init__(self, camp, user, gender, number_of_visits):
        self.camp = camp
        self.user = user
        self.gender = gender
        self.number_of_visits = number_of_visits

But I've got an error

UPDATE statement on table 'scouts' expected to update 1 row(s); 1001 were matched

where instance.number_of_visits equal to 1, it's not a list of rows or something like that.

来源：https://stackoverflow.com/questions/37796909/cannot-update-table-via-sqlalchemy