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The method to inform Sqlalchemy that the object is already present is to use the merge() method. This method takes an object as an argument and merges it with the session's state, so that any changes made to the object are tracked by the session. If the object already exists in the database, it will be updated with the new data. If it doesn't exist yet, a new row will be created in the database with the data from the object. Here's an example:

from sqlalchemy.orm import sessionmaker
from myapp.models import MyObject
Session = sessionmaker(bind=engine)
session = Session()
obj = session.query(MyObject).get(1)  # get an existing object from the database
# make some changes to the object
obj.name = 'New Name'
# merge the object with the session's state
session.merge(obj)
session.commit()  # commit the changes to the database

In this example, the merge() method is used to update an existing object in the database with a new name. If the object didn't exist yet, a new row would be created with the name 'New Name'.