try_fix_sqlakeyset.py

import sqlalchemy as sa
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()


class Test(Base):
    __tablename__ = 'test'

    id = sa.Column('test_id', sa.Integer, primary_key=True)


# we have only column and instance
some_col = Test.__table__.c.test_id

t = Test()
t.id = 1

# now try find value in instance by column

col_name = some_col.name
try:
    getattr(t, col_name) # bug in sqlakeyset
except AttributeError:
    print('attr err')  # error sad but true

from sqlalchemy.orm import object_mapper

mapper = object_mapper(t)

col_property = mapper.get_property_by_column(some_col)

val = getattr(t, col_property.key)

assert val == t.id