How to change postgresql datetime to string?

model

class CalendarEvent(db.Model):
    __tablename__ = 'CalendarEvent'

    id = Column(Integer, primary_key=True)
    ce_title = Column(String(100))
    ce_content = Column(Text, nullable=True)
    ce_start = Column(DateTime)
    ce_end = Column(DateTime, nullable=True)
    ce_all_day = Column(Boolean, default=False)
    ce_color = Column(String(10))
    ce_delete = Column(Boolean, default=False)

query

events = CalendarEvent.query.filter(CalendarEvent.ce_delete == False).all()

I want change datetime to string.

CalendarEvent.ce_start -> "2020-11-25T12:00:00"

How to change?