python flask sqlite error?

Question

SQLite

My app code

from flask import Flask, render_template, url_for
from flask_sqlalchemy import SQLAlchemy
from datetime import datetime

app= Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URL'] = 'sqlite://blog.db'
db = SQLAlchemy(app)


class Article(db.Model):
    id = db.Column(db.Integer, nullable=True)
    id = db.Column(db.String(100), nullable=False)
    id = db.Column(db.String(300), nullable=False)
    id = db.Column(db.Text, nullable=False)
    id = db.Column(db.DateTime, default=datetime.utcnow)

    def __repr__(self):
        return '<Article %r>' % self.id

my error when calling from app import db

C:\Users\никита\Desktop\app>python Python 3.6.0 (v3.6.0:41df79263a11, Dec 23 2016, 08:06:12) [MSC v.1900 64 bit (AMD64)] on win32 Type "help", "copyright", "credits" or "license" for more information. >>> from app import db C:\Users\никита\AppData\Local\Programs\Python\Python36\lib\site-packages\flask_sqlalchemy\__init__.py:852: UserWarning: Neither SQLALCHEMY_DATABASE_URI nor SQLALCHEMY_BINDS is set. Defaulting SQLALCHEMY_DATABASE_URI to "sqlite:///:memory:". 'Neither SQLALCHEMY_DATABASE_URI nor SQLALCHEMY_BINDS is set. ' C:\Users\никита\AppData\Local\Programs\Python\Python36\lib\site-packages\flask_sqlalchemy\__init__.py:873: FSADeprecationWarning: SQLALCHEMY_TRACK_MODIFICATIONS adds significant overhead and will be disabled by default in the future. Set it to True or False to suppress this warning. 'SQLALCHEMY_TRACK_MODIFICATIONS adds significant overhead and ' Traceback (most recent call last): File "<stdin>", line 1, in <module> File "C:\Users\никита\Desktop\app\app.py", line 10, in <module> class Article(db.Model): File "C:\Users\никита\AppData\Local\Programs\Python\Python36\lib\site-packages\flask_sqlalchemy\model.py", line 67, in __init__ super(NameMetaMixin, cls).__init__(name, bases, d) File "C:\Users\никита\AppData\Local\Programs\Python\Python36\lib\site-packages\flask_sqlalchemy\model.py", line 121, in __init__ super(BindMetaMixin, cls).__init__(name, bases, d) File "C:\Users\никита\AppData\Local\Programs\Python\Python36\lib\site-packages\sqlalchemy\orm\decl_api.py", line 72, in __init__ _as_declarative(reg, cls, dict_) File "C:\Users\никита\AppData\Local\Programs\Python\Python36\lib\site-packages\sqlalchemy\orm\decl_base.py", line 126, in _as_declarative return _MapperConfig.setup_mapping(registry, cls, dict_, None, {}) File "C:\Users\никита\AppData\Local\Programs\Python\Python36\lib\site-packages\sqlalchemy\orm\decl_base.py", line 177, in setup_mapping return cfg_cls(registry, cls_, dict_, table, mapper_kw) File "C:\Users\никита\AppData\Local\Programs\Python\Python36\lib\site-packages\sqlalchemy\orm\decl_base.py", line 326, in __init__ self._early_mapping(mapper_kw) File "C:\Users\никита\AppData\Local\Programs\Python\Python36\lib\site-packages\sqlalchemy\orm\decl_base.py", line 209, in _early_mapping self.map(mapper_kw) File "C:\Users\никита\AppData\Local\Programs\Python\Python36\lib\site-packages\sqlalchemy\orm\decl_base.py", line 1004, in map mapper_cls(self.cls, self.local_table, **self.mapper_args), File "<string>", line 2, in __init__ File "C:\Users\никита\AppData\Local\Programs\Python\Python36\lib\site-packages\sqlalchemy\util\deprecations.py", line 298, in warned return fn(*args, **kwargs) File "C:\Users\никита\AppData\Local\Programs\Python\Python36\lib\site-packages\sqlalchemy\orm\mapper.py", line 685, in __init__ self._configure_pks() File "C:\Users\никита\AppData\Local\Programs\Python\Python36\lib\site-packages\sqlalchemy\orm\mapper.py", line 1373, in _configure_pks % (self, self.persist_selectable.description) sqlalchemy.exc.ArgumentError: Mapper mapped class Article->article could not assemble any primary key columns for mapped table 'article'