sqlalchemy.exc.OperationalError: (OperationalError) unable to open database file None None

Question

I am running a program from another person who are inconvenience ask for help from. The program is a website. Server end is written by python and flask (module, http://flask.pocoo.org/). The program has been successfully run on the server. What I need to do is modify something on it. Since the production server is not allowed for test, I tested it in development server locally via flask. However, I could not run even the original program. Below is from python.

(venv)kevin@ubuntu:~/python/public_html$ python index.wsgi 

Traceback (most recent call last): File "index.wsgi", line 6, in from app import app as application

File "/home/kevin/python/public_html/app.py", line 27, in <module>
app = create_app()

File "/home/kevin/python/public_html/app.py", line 12, in create_app
database.init_db()

File "/home/kevin/python/public_html/database.py", line 24, in init_db
Base.metadata.create_all(engine)

File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/schema.py", line 2793, in create_all
  tables=tables)
File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 1478, in _run_visitor
with self._optional_conn_ctx_manager(connection) as conn:

File "/usr/lib/python2.7/contextlib.py", line 17, in __enter__
return self.gen.next()

File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 1471, in _optional_conn_ctx_manager
with self.contextual_connect() as conn:

File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 1661, in contextual_connect
self.pool.connect(),

File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/pool.py", line 272, in connect
return _ConnectionFairy(self).checkout()

File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/pool.py", line 425, in __init__
rec = self._connection_record = pool._do_get()

File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/pool.py", line 857, in _do_get
return self._create_connection()

File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/pool.py", line 225, in _create_connection
return _ConnectionRecord(self)

File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/pool.py", line 318, in __init__
self.connection = self.__connect()

File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/pool.py", line 368, in __connect
connection = self.__pool._creator()

File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/strategies.py", line 80, in connect
return dialect.connect(*cargs, **cparams)

File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/default.py", line 283, in connect
return self.dbapi.connect(*cargs, **cparams)

sqlalchemy.exc.OperationalError: (OperationalError) unable to open database file None None

In the config.py file

LOGFILE = '/tmp/ate.log' DEBUG = True TESTING = True THREADED = True DATABASE_URI = 'sqlite:////tmp/ate.db' SECRET_KEY = os.urandom(24)

Hence, I created a folder called "tmp" under my user and an empty file called "ate.db". Then, ran it again. It said

IOError: [Errno 2] No such file or directory: '/home/kevin/log/ate.log'

Then, I created the log folder and the log file. Run it, but nothing happened like

(venv)kevin@ubuntu:~/python/public_html$ python index.wsgi (venv)kevin@ubuntu:~/python/public_html$ python index.wsgi (venv)kevin@ubuntu:~/python/public_html$

If it is successful, the website should be available on http://127.0.0.1:5000/. However, it did not work. Does anybody know why and how to solve it? The codes should be fine since it is now available online. The problem should be a local problem. Thank you so much for your help.

The code of where the program is stuck

from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import scoped_session, sessionmaker

engine = None
db_session = None
Base = declarative_base()


def init_engine(uri, **kwards):
    global engine
    engine = create_engine(uri, **kwards)
    return engine


def init_db():
    global db_session
    db_session = scoped_session(sessionmaker(bind=engine))
    # import all modules here that might define models so that
    # they will be registered properly on the metadata.  Otherwise
    # you will have to import them first before calling init_db()
    import models
    Base.metadata.create_all(engine)

Answer 1

This is the problem related to your file path. If you want to save your file in your root directory itself, then write file_name itself right after '/' -

app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///file_name.db'

Answer 2

I was able to overcome the same error by running sudo python :)

Answer 3

I am doing a course of Python and I have the same problem. Affortunately in the course put the right way to determined the path of the database URI

So it works for me even in the 2022 year.

You need to change:

app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:////tmp/test.db'

to:

app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///<name of database>.db'

I hope that it works for someone.

Answer 4

I had this same issue when trying to start the central scheduler for luigi (python module) with task history enabled.

sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) unable to open database file

I was attempting to use the following configuration from their documentation:

[task_history]
db_connection = sqlite:////user/local/var/luigi-task-hist.db

However, /user/local/* did not exist on my machine and I had to change the configuration to:

[task_history]
db_connection = sqlite:////usr/local/var/luigi-task-hist.db

Kind of a dumb mistake, but easily overlooked. Might save someone some time. This change got rid of the error in my case and luigid started with no errors.

Answer 5

For those looking for a solution to the OperationalError, not necessarily caused by being unable to open database file None None - you might try adding a pool_pre_ping=True argument to create_engine, i.e.

engine = create_engine("mysql+pymysql://user:pw@host/db", pool_pre_ping=True)

see sqlalchemy documentation:

Pessimistic testing of connections upon checkout is achievable by using the Pool.pre_ping argument, available from create_engine() via the create_engine.pool_pre_ping argument

The “pre ping” feature will normally emit SQL equivalent to “SELECT 1” each time a connection is checked out from the pool; if an error is raised that is detected as a “disconnect” situation, the connection will be immediately recycled, and all other pooled connections older than the current time are invalidated, so that the next time they are checked out, they will also be recycled before use.

Answer 6

You're not managing to find the path to the database from your current level. What you need to do is the following:

DATABASE_URI = 'sqlite:///../tmp/ate.db'

That means go up to the root level .. and then navigate down to the database (the relative path is /tmp/ate.db in this case).

Answer 7

Replace:

app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:////dbdir/test.db'

With:

app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///dbdir/test.db'

Answer 8

finally figured it out, had help tho

 import os

file_path = os.path.abspath(os.getcwd())+"\database.db"

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///'+file_path
 db = SQLAlchemy(app)

Answer 9

I just met this same problem and found that I make a stupid circular reference .

./data_model.py

from flask.ext.sqlalchemy import SQLAlchemy
from api.src.app import app

app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:////database/user.db')

db = SQLAlchemy(app)

./app.py

...
from api.src.data_model import db
db.init_app(app)

Then I removed the app.py/db and it works.

Answer 10

My database URI started rocking after adding one dot in between ////. Working on windows 7. I had directory and db-file created prior to calling this.

app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///./dbdir/test.db'

Answer 11

I had this issue with sqlite. The process trying to open the database file needs to have write access to the directory as it creates temporary/lock files.

The following structure worked for me to allow www-data to use the database.

%> ls -l
drwxrwxr-x  2 fmlheureux www-data     4096 Feb 17 13:24 database-dir

%> ls -l database-dir/
-rw-rw-r-- 1 fmlheureux www-data 40960 Feb 17 13:28 database.sqlite

Answer 12

I think I've seen errors like this where file permissions were wrong for the .db file or its parent directory. You might make sure that the process trying to access the database can do so by appropriate use of chown or chmod.

This is specifically about Django, but maybe still relevant: https://serverfault.com/questions/57596/why-do-i-get-sqlite-error-unable-to-open-database-file