Python db.create_all（）不'；t创建在单独文件中定义的表

我正在尝试为我的模型创建表，这些模型是在我的应用程序的单独模块中定义的。我调用了db.create_all（），但没有创建任何表，也没有错误。我已经定义了模型和。为什么这样不行

from flask import Flask
from flask.ext.sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'postgresql+psycopg2://postgres:123@localhost/flask'
db = SQLAlchemy(app)

from models import User

db.create_all()
db.session.commit()

models.py

：

from flask.ext.sqlalchemy import SQLAlchemy

db = SQLAlchemy()

class User(db.Model):
  __tablename__ = 'users'
  uid = db.Column(db.Integer, primary_key = True)

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
db = SQLAlchemy(app)

# import the models *after* the db object is defined
from myapp import models

from myapp import db

class User(db.Model):
    ...

from myapp import app, db

with app.app_context():
    db.create_all()

---

您创建了两个单独的db实例，一个与应用程序一起创建，另一个与模型一起创建。每个实例都有自己的元数据，用于存储在其上定义的表。您用来发出CREATETABLE语句的不是定义模型的那个。您应该只使用扩展的一个实例，在需要时导入它

myapp/\uuuuuu init\uuuuuuuu.py

：

from flask.ext.sqlalchemy import SQLAlchemy

db = SQLAlchemy()

class User(db.Model):
  __tablename__ = 'users'
  uid = db.Column(db.Integer, primary_key = True)

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
db = SQLAlchemy(app)

# import the models *after* the db object is defined
from myapp import models

from myapp import db

class User(db.Model):
    ...

from myapp import app, db

with app.app_context():
    db.create_all()

myapp/models.py

：

from flask.ext.sqlalchemy import SQLAlchemy

db = SQLAlchemy()

class User(db.Model):
  __tablename__ = 'users'
  uid = db.Column(db.Integer, primary_key = True)

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
db = SQLAlchemy(app)

# import the models *after* the db object is defined
from myapp import models

from myapp import db

class User(db.Model):
    ...

from myapp import app, db

with app.app_context():
    db.create_all()

create_tables.py

：

from flask.ext.sqlalchemy import SQLAlchemy

db = SQLAlchemy()

class User(db.Model):
  __tablename__ = 'users'
  uid = db.Column(db.Integer, primary_key = True)

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
db = SQLAlchemy(app)

# import the models *after* the db object is defined
from myapp import models

from myapp import db

class User(db.Model):
    ...

from myapp import app, db

with app.app_context():
    db.create_all()

---

其他需要注意的事项：

• 你应该将你的应用程序组织成一个包，这样所有东西都可以在一个位置下导入

• flask.ext

  已弃用，请直接从其包名导入扩展名
• Flask SQLAlchemy根据类名自动生成

  \uuuuuuuuuuuuuuuuuuuuuuuu

  ，您不需要自己定义它
• 您不必在

  create\u all

  之后调用

  commit