Question

我正在尝试使用this tutorial进行第一次数据库迁移。区别在于作者从头开始，而我已经有一个MySQL数据库。

但是，正如作者在其教程中所做的那样，我在app/models.py中编写了新的数据库模型：

from app import db

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(64), index=True, unique=True)
    email = db.Column(db.String(120), index=True, unique=True)
    password_hash = db.Column(db.String(128))

    def __repr__(self):
        return '<User {}>'.format(self.username)

它将包括映射到Flask应用程序的User数据库模型的users表。

我担心数据库迁移脚本为空，而flask db migration命令似乎并未创建数据库。因此，我尝试使用解释器进行操作：

>>> from app import db
>>> from app.models import User, Post
>>> u = User(username='john', email='john@example.com')
>>> db.session.add(u)
>>> db.session.commit()
Traceback (most recent call last):
  File "/home/mike/.local/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1193, in _execute_context
    context)
  File "/home/mike/.local/lib/python3.6/site-packages/sqlalchemy/engine/default.py", line 509, in do_execute
    cursor.execute(statement, parameters)
sqlite3.OperationalError: no such table: user

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/mike/.local/lib/python3.6/site-packages/sqlalchemy/orm/scoping.py", line 153, in do
    return getattr(self.registry(), name)(*args, **kwargs)
  File "/home/mike/.local/lib/python3.6/site-packages/sqlalchemy/orm/session.py", line 943, in commit
    self.transaction.commit()
...
...
  File "/home/mike/.local/lib/python3.6/site-packages/sqlalchemy/engine/default.py", line 509, in do_execute
    cursor.execute(statement, parameters)
sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) no such table: user [SQL: 'INSERT INTO user (username, email, password_hash) VALUES (?, ?, ?)'] [parameters: ('john', 'john@example.com', None)] (Background on this error at: http://sqlalche.me/e/e3q8)
Error in sys.excepthook:
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/apport_python_hook.py", line 63, in apport_excepthook
    from apport.fileutils import likely_packaged, get_recent_crashes
  File "/usr/lib/python3/dist-packages/apport/__init__.py", line 5, in <module>
...
    from apport.packaging_impl import impl as packaging
  File "/usr/lib/python3/dist-packages/apport/packaging_impl.py", line 23, in <module>
    import apt
  File "/usr/lib/python3/dist-packages/apt/__init__.py", line 23, in <module>
    import apt_pkg
ModuleNotFoundError: No module named 'apt_pkg'

Original exception was:
Traceback (most recent call last):
  File "/home/mike/.local/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1193, in _execute_context
    context)
  File "/home/mike/.local/lib/python3.6/site-packages/sqlalchemy/engine/default.py", line 509, in do_execute
    cursor.execute(statement, parameters)
sqlite3.OperationalError: no such table: user

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/mike/.local/lib/python3.6/site-packages/sqlalchemy/orm/scoping.py", line 153, in do
    return getattr(self.registry(), name)(*args, **kwargs)
...
  File "/home/mike/.local/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1193, in _execute_context
    context)
  File "/home/mike/.local/lib/python3.6/site-packages/sqlalchemy/engine/default.py", line 509, in do_execute
    cursor.execute(statement, parameters)
sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) no such table: user [SQL: 'INSERT INTO user (username, email, password_hash) VALUES (?, ?, ?)'] [parameters: ('john', 'john@example.com', None)] (Background on this error at: http://sqlalche.me/e/e3q8)

我该如何创建数据库并处理此问题？

这是我的config.py文件

import os
basedir = os.path.abspath(os.path.dirname(__file__))

class Config(object):
    # ...
    SQLALCHEMY_DATABASE_URI = os.environ.get('DATABASE_URL') or \
        'sqlite:///' + os.path.join(basedir, 'app.db')
    SQLALCHEMY_TRACK_MODIFICATIONS = False

Answer 1

我必须按照Everilä先生的说法在命令行中编码db.create_all()，即使它不是本教程中编写的

无法使用sqlalchemy和sqlite从模型创建表

1 个答案: