I am writing my first Python web application, and I want to use alembic for handling the migrations. So far I have done this (just pointing out the imp. files) and it doesn't seem to work.
Project structure:
project/
alembic.ini
alembic/
versions/
3cd4a4f9cdef_create_users_table.py
models/
__init__.py
base.py
users.py
3cd4a4f9cdef_create_users_table.py
"""create users table
Revision ID: 3cd4a4f9cdef
Revises:
Create Date: 2016-09-07 13:54:25.705084
"""
# revision identifiers, used by Alembic.
revision = '3cd4a4f9cdef'
down_revision = None
branch_labels = None
depends_on = None
from alembic import op
import sqlalchemy as sa
def upgrade():
op.create_table(
'users',
Column('id', sa.Integer, primary_key=True),
Column('name', sa.String(256), nullable=False)
)
def downgrade():
op.drop_table('users')
__init__.py
from sqlalchemy import create_engine
from sqlalchemy.sql import select
from users import User
engine = create_engine('sqlite:///:memory:', echo=True)
base.py
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
users.py
from base import Base
class User(Base):
user_table = 'users'
__table__ = user_table
id = user_table.c.id
name = user_table.c.name
$ python models/__init__.py throws this error:
Traceback (most recent call last):
File "models/__init__.py", line 3, in <module>
from users import User
File "/Users/sudeep.agarwal/src/project/models/users.py", line 5, in <module>
class Asset(Base):
File "/Users/sudeep.agarwal/src/squiddy/models/users.py", line 10, in Asset
id = asset_table.c.id
AttributeError: 'str' object has no attribute 'c'
I don't want to do this in users.py as it would mean duplication of schema definition:
from base import Base
from sqlalchemy import Column
class User(Base):
__table__ = 'users'
id = Column('id', Integer, primary_key=True)
name = Column('name', String, nullable=False)
What is the cleanest way to achieve this?
Frankly, I do not quite understand what you're trying to do. But some parts of code looks completely wrong. Why have you two definitions of User? What are you trying to achieve with id = user_table.c.id? I can only guess. At first, define somewhere table schema:
metadata = MetaData()
users_schema = Table('users', metadata,
Column('id', Integer, primary_key=True),
Column('name', String, nullable=False)
)
Then you can use it to define the model:
class User(Base):
__table__ = users_schema
Or you can define the model directly:
class User(Base):
__tablename__ = 'users'
id = Column('id', Integer, primary_key=True)
name = Column('name', String, nullable=False)
And you do not need to redefine it in other files. Only import it and use.