Seperate database model files with flask and sqlalchemy and alembic

app.py

from flask import Flask
from services.database import db

app = Flask(module_name)

db.init_app(app)

attachment.py

class Attachment(db.Model):
    """
    table attachement
    """

    id = db.Column(db.String(50), primary_key=True)
    """:type : str"""

    name = db.Column(db.String(200))
    """:type : str"""

    content = db.Column(db.Binary)
    """:type : bytearray"""

    created = db.Column(db.DateTime, default=datetime.datetime.now)
    """:type : datetime"""

    content_type = db.Column(db.String(100))
    """:type : str"""

    def __init__(self, name, content, content_type):
        """
        
        :param content:
        :type content: bytearray
        :param name:
        :type name: str
        :param content_type:
        :type content_type: str
        :return:
        :rtype:
        """
        self.id = uuid.uuid4().hex
        self.name = name
        self.content = content
        self.content_type = content_type

database.py

from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()

env.py

# this is alembic env.py file, just edit something like below

# add your model's MetaData object here
# for 'autogenerate' support
# from myapp import mymodel
# target_metadata = mymodel.Base.metadata
import sys
import os

sys.path.append(os.getcwd())

from core.configuration import config as sys_config
from services.database import db

# this path is your db_models py files path
path = os.path.join(sys_config.project_root, 'services', 'db_models')

# import all db_models, so the db.metadata will have data
for py in [f[:-3] for f in os.listdir(path) if f.endswith('.py') and f != '__init__.py']:
    mod = __import__('.'.join(['services.db_models', py]), fromlist=[py])
    classes = [getattr(mod, x) for x in dir(mod) if isinstance(getattr(mod, x), type)]
    for cls in classes:
        if 'flask_sqlalchemy.' in str(type(cls)):
            print("auto import db model: {0}".format(cls))
            setattr(sys.modules[__name__], cls.__name__, cls)
target_metadata = db.metadata

# sepcial the sqlalchemy.url read form our config file
config.set_main_option('sqlalchemy.url', sys_config.SQLALCHEMY_DATABASE_URI)

kb.py

class KBInfo(db.Model):
    """
    kb info
    """
    id = db.Column(db.String(50), primary_key=True)
    """:type : str"""

    title = db.Column(db.String(200), nullable=False)
    """:type : str"""

    content = db.Column(db.Text())
    """:type : str"""

    author = db.Column(db.String(200))
    """:type : str"""

    created = db.Column(db.DateTime, default=datetime.datetime.now)
    """:type : datetime"""

    modified = db.Column(db.DateTime, default=datetime.datetime.now)
    """:type : datetime"""

    is_public = db.Column(db.Boolean)
    """:type : bool"""

    def __init__(self, title, content, is_public, author):
        self.id = uuid.uuid4().hex
        self.title = title
        self.content = content
        self.is_public = is_public
        self.author = author

Excellent.