SQLAlchemy db.create_all() demo fails
flask, python, sqlalchemy, sqlite
Solution
You are using Windows, and there is no `/tmp` temporary directory in Windows. The database connection fails because SQLite3 has no directory to create the database file in. Pick a different location for your database file.
In this case, you could use `tempfile.gettempdir()` to build a path:
import tempfile
import os.path
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///' + os.path.join(
tempfile.gettempdir(), 'test.db')
Problem
I am following the tutorial from this page: https://pythonhosted.org/Flask-SQLAlchemy/quickstart.html I believe I did it exactly line for line. But I get an error each time when I try to db.create_all() Here is my code (I moved the actual db.create_all() to be part of the file for simplicity here, though I've tried it the way the tutorial shows as well at the command line. ``` from flask import Flask from flask.ext.sqlalchemy import SQLAlchemy app = Flask(__name__) app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:////tmp/test.db' db = SQLAlchemy(app) class User(db.Model): id = db.Column(db.Integer, primary_key=True) username = db.Column(db.String(80), unique=True) email = db.Column(db.String(120), unique=True) def __init__(self, username, email): self.username = username self.email = email def __repr__(self): return '<User %r>' % self.username db.create_all() ``` I found a similar question on Stack Overflow at Flask SQLAlchemy db.create_all() not creating database and SQLAlchemy create_all() does not create tables But that response didn't help me. (In fact the answer to the second one seems to have a serious bug) This is all in Python 3.4 The error I get is very long, but here it is: ``` Traceback (most recent call last): File "C:\Programming\LearningFlask\FlaskCookbook\test_create_db\python\lib\site-packages\sqlalchemy\engine\strategies.py", line 90, in connect return dialect.connect(*cargs, **cparams) File "C:\Programming\LearningFlask\FlaskCookbook\test_create_db\python\lib\site-packages\sqlalchemy\engine\default.py", line 377, in connect return self.dbapi.connect(*cargs, **cparams) sqlite3.OperationalError: unable to open database file The above exception was the direct cause of the following exception: Traceback (most recent call last): File "<pyshell#2>", line 1, in <module> import test_create_db.py File "C:\Programming\LearningFlask\FlaskCookbook\test_create_db\python\test_create_db.py", line 25, in <module> db.create_all() File "C:\Programming\LearningFlask\FlaskCookbook\test_create_db\python\lib\site-packages\flask_sqlalchemy\__init__.py", line 895, in create_all self._execute_for_all_tables(app, bind, 'create_all') File "C:\Programming\LearningFlask\FlaskCookbook\test_create_db\python\lib\site-packages\flask_sqlalchemy\__init__.py", line 887, in _execute_for_all_tables op(bind=self.get_engine(app, bind), **extra) File "C:\Programming\LearningFlask\FlaskCookbook\test_create_db\python\lib\site-packages\sqlalchemy\sql\schema.py", line 3404, in create_all tables=tables) File "C:\Programming\LearningFlask\FlaskCookbook\test_create_db\python\lib\site-packages\sqlalchemy\engine\base.py", line 1615, in _run_visitor with self._optional_conn_ctx_manager(connection) as conn: File "C:\Python34\Lib\contextlib.py", line 59, in __enter__ return next(self.gen) File "C:\Programming\LearningFlask\FlaskCookbook\test_create_db\python\lib\site-packages\sqlalchemy\engine\base.py", line 1608, in _optional_conn_ctx_manager with self.contextual_connect() as conn: File "C:\Programming\LearningFlask\FlaskCookbook\test_create_db\python\lib\site-packages\sqlalchemy\engine\base.py", line 1798, in contextual_connect self.pool.connect(), File "C:\Programming\LearningFlask\FlaskCookbook\test_create_db\python\lib\site-packages\sqlalchemy\pool.py", line 338, in connect return _ConnectionFairy._checkout(self) File "C:\Programming\LearningFlask\FlaskCookbook\test_create_db\python\lib\site-packages\sqlalchemy\pool.py", line 644, in _checkout fairy = _ConnectionRecord.checkout(pool) File "C:\Programming\LearningFlask\FlaskCookbook\test_create_db\python\lib\site-packages\sqlalchemy\pool.py", line 440, in checkout rec = pool._do_get() File "C:\Programming\LearningFlask\FlaskCookbook\test_create_db\python\lib\site-packages\sqlalchemy\pool.py", line 1057, in _do_get return self._create_connection() File "C:\Programming\LearningFlask\FlaskCookbook\test_create_db\python\lib\site-packages\sqlalchemy\pool.py", line 285, in _create_connection return _ConnectionRecord(self) File "C:\Programming\LearningFlask\FlaskCookbook\test_create_db\python\lib\site-packages\sqlalchemy\pool.py", line 411, in __init__ self.connection = self.__connect() File "C:\Programming\LearningFlask\FlaskCookbook\test_create_db\python\lib\site-packages\sqlalchemy\pool.py", line 538, in __connect connection = self.__pool._creator() File "C:\Programming\LearningFlask\FlaskCookbook\test_create_db\python\lib\site-packages\sqlalchemy\engine\strategies.py", line 96, in connect connection_invalidated=invalidated File "C:\Programming\LearningFlask\FlaskCookbook\test_create_db\python\lib\site-packages\sqlalchemy\util\compat.py", line 188, in raise_from_cause reraise(type(exception), exception, tb=exc_tb, cause=exc_value) File "C:\Programming\LearningFlask\FlaskCookbook\test_create_db\python\lib\site-packages\sqlalchemy\util\compat.py", line 181, in reraise raise value.with_traceback(tb) File "C:\Programming\LearningFlask\FlaskCookbook\test_create_db\python\lib\site-packages\sqlalchemy\engine\strategies.py", line 90, in connect return dialect.connect(*cargs, **cparams) File "C:\Programming\LearningFlask\FlaskCookbook\test_create_db\python\lib\site-packages\sqlalchemy\engine\default.py", line 377, in connect return self.dbapi.connect(*cargs, **cparams) sqlalchemy.exc.OperationalError: (OperationalError) unable to open database file None None ```